This work was supported by a grant from the National Science Foundation (MCB-0923794 to FT).

1. Producing Perithecia
<ol>
	<li>Center inoculate carrot agar10 in a 6.0 cm diam Petri dish with a fertile strain of F. graminearum (Recommend PH-1).</li>
	<li>Place inoculated dishes under bright fluorescent lights at room temperature (18-24 &deg;C) and allow to grow until mycelium has reached the outer edge of the Petri dish (3-5 days). Commercial household fluorescent lights work fine for stimulating fruiting body formation and discharge.</li>
	<li>Gently remove the aerial mycelia with a sterile toothpick.</li>
	<li>Distribute 1.0 ml 2.5 % Tween 60 aq to the surface with a sterile glass hockeystick or rounded end of a sterile glass rod.</li>
	<li>Return plates to light. Do not add Parafilm to plates.</li>
	<li>After 24 hr, the surface of the plates should have a shiny appearance. If mycelia reappears, scrape surface and re-apply Tween-60 solution.</li>
	<li>Observe development of perithecia over the next week. The intermediate stages of perithecium development can be harvested by gently scraping the surface of the agar and flash frozen for RNA extraction (Figure 1).</li>
	<li>Mature spores will accumulate on the lid of the plate by day 7. Initially these will only be visible under a dissecting microscope, but by day 9, they will have accumulated to sufficient density so as to be visible to the naked eye.</li>
</ol>
2. Ascospore Discharge Assay
<ol>
	<li>On day 6 after application of Tween solution, cut a 1 cm diam circle out of the agar with a wood borer. Alternatively, a scalpel can be used to remove a similar sized segment. The circle can be sliced in half and each half placed on a glass microscope slide.</li>
	<li>Orient the pieces so the surface containing the fruiting bodies is perpendicular to the surface of the slide, and the spores are fired down the length of the slide.</li>
	<li>Place the slide in a humidity chamber overnight under lights. Spores will accumulate on the slide and be visible to the naked eye the next morning (Figure 2).</li>
	<li>Accumulated spores may be washed off the slide with water and quantified if desired.</li>
	<li>Potential ascospore discharge inhibitors can be assayed by adding them to the back side of the agar block during assembly of the assay. Some ion channel inhibitors that reduce discharge have been previously assayed with this technique15.</li>
</ol>
3. Generation of Recombinant Progeny
<ol>
	<li>Initiate cross by inoculating carrot agar with two strains of F. graminearum (one Nit+ and one nit-), placing the inoculation points on opposite sides of the Petri dish.</li>
	<li>Once hyphae have filled the surface, scrape off aerial portion and apply Tween-60 solution as described above. Use a marker to note on the side of the Petri dish where the hyphae meet.</li>
	<li>Return cultures to light and incubate until perithecia have developed, and cirrhi have begun to form from the perithecia along the intersection between the two cultures.</li>
	<li>Under the dissecting microscope, bring into view the perithecia along the intersection of the two cultures. Using an insect pin, sterilized and dipped into sterile water, touch a cirrhus along this border lightly with the tip of the pin. The moisture on the pin should allow the cirrhus to stick to the pin.</li>
	<li>Rinse the tip of the pin with the cirrhus on it in 200 &mu;l sterile water in an Eppendorf tube to wash the spores off.</li>
	<li>Flame the pin, moisten it again and pick another cirrhus. Pick 10 to 15 cirrhi, and place each in a separate tube of water.</li>
	<li>Briefly vortex tubes containing suspended cirrhi.</li>
	<li>Remove 60 &mu;l of the spore suspension with a pipette and place on MMTS medium1 in a 9 cm Petri dish. Spread with a sterile hockey stick. The remaining spore suspension may be stored at 4 &deg;C for up to a week and replated if necessary.</li>
	<li>Incubate at room temperature (light not necessary) for 3-5 days until very small colonies appear (Figure 3). There will be two kinds of phenotypes among the colonies. The nit- colonies will have sparser hyphae than the Nit+ colonies. Cirrhi from recombinant perithecia will show both colony phenotypes in approximately equal proportion. Discard the plates with colonies of only a single phenotype on them. Note that sometimes more than two phenotypes result due to segregation of other factors.</li>
	<li>Move colonies to V8 or carrot agar for storage. Test colonies on Czapek's Dox Agar (the nit- strains will not grow on Czapek's Dox) and on PDA with Chlorate (0.5 M Potassium Chlorate; the Nit+ strains will not grow on PDA with Chlorate) to confirm the correct phenotype. Examine these colonies for the desired qualities.</li>
</ol>
4. Representative Results
Producing perithecia
The goal is to have a lawn of perithecia without any mycelia or spores apparent. The surface of the culture will appear similar to black velvet (Figure 1). At 24 hr after the application of Tween the surface of the agar should have a slight sheen. If mycelia reappear, then the plate may not have been scraped enough to induce perithecium development.
Ascospore discharge
Always provide in your assay several blocks of agar from the wild-type strain. If those do not fire, then either your perithecia are too young or too old. If they are too old, then numerous hyphae will appear over the surface of the culture giving it a whitish hue. If this is not the case, they may be too young, and the assay should be tried again in 24 hr. Occasionally, cultures do not discharge well, and the experiment will have to be repeated. Be sure you perform the assay under the proper light conditions.
Recombinant progeny
Recombinant perithecia should make up the majority of perithecia along the intersection between the two strains. We usually process 10 cirrhi from a cross and at least 4-6 of those should be recombinant. Very occasionally, a mutation prevents a strain from mating. If one of the parents has an aberrant growth phenotype, then more than 2 phenotypes may be present among the colonies on MMTS.
<img alt="Figure 1" src="/files/ftp_upload/3895/3895fig1.jpg" /> 
Figure 1. Stages of perithecium development on carrot agar. Left, 72 h after application of Tween. Note red pigment and very young perithecia visible as a black grains on the surface. Right, at 144 h, mature perithecia have formed. Note near-complete absence of superficial mycelia in both cultures.
<img alt="Figure 2" src="/files/ftp_upload/3895/3895fig2.jpg" /> 
Figure 2. Discharge assay. The orange carrot agar plug is oriented so that spores forcibly discharged from the mature perithecia on its surface can accumulate on the surface of the glass slide. 15 hr accumulation time.
<img alt="Figure 3" src="/files/ftp_upload/3895/3895fig3.jpg" /> 
Figure 3. Differences in growth between Nit+ and nit- colonies on selective MMTS medium. The nit- colonies (arrowheads) are smaller. The Nit+ colonies (arrows) show robust growth. Photograph taken after 7 days.

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	<li>Bowden, R. L., Leslie, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sexual+recombination+in+Gibberella+zeae.">Sexual recombination in Gibberella zeae.</a> Phytopathology. 89, 182-188 (1999).</li><li>Buller, A. H. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Researches on Fungi. , (1909).</li><li>Cavinder, B., Hamam, A., Lew, R. R., Trail, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mid1,+a+mechanosensitive+calcium+ion+channel,+affects+growth,+development,+and+ascospore+discharge+in+the+filamentous+fungus+Gibberella+zeae.">Mid1, a mechanosensitive calcium ion channel, affects growth, development, and ascospore discharge in the filamentous fungus Gibberella zeae.</a> Eukaryotic Cell. 10, 832-841 (2011).</li><li>Cuomo, C., Güldener, U., Xu, J. R., Trail, F., Turgeon, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Fusarium+graminearum+genome+reveals+a+link+between+localized+polymorphism+and+pathogen+specialization.">The Fusarium graminearum genome reveals a link between localized polymorphism and pathogen specialization.</a> Science. 317, 1400-1402 (2007).</li><li>Desjardins, A. E., Brown, D. W., Yun, S. -. H., Proctor, R. H., Lee, T., Plattner, R. D., Lu, S. -. W., Turgeon, B. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deletion+and+complementation+of+the+mating+type+(MAT)+locus+of+the+wheat+head+blight+pathogen+Gibberella+zeae.">Deletion and complementation of the mating type (MAT) locus of the wheat head blight pathogen Gibberella zeae.</a> Applied and Environmental Microbiology. 70, 2437-2444 (2004).</li><li>Gueldener, U., Seong, K. -. Y., Boddu, J., Cho, S., Trail, F., Xu, J. -. R., Adam, G., Mewes, H. -. W., Muehlbauer, G. J., Kistler, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+Fusarium+graminearum+Affymetrix+GeneChip+For+profiling+fungal+gene+expression+in+vitro+and+in+planta.">Development of a Fusarium graminearum Affymetrix GeneChip For profiling fungal gene expression in vitro and in planta.</a> Fungal Genetics and Biology. 43, 316-325 (2006).</li><li>Hallen, H., Trail, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+L-Type+calcium+ion+channel+Cch1+affects+ascospore+discharge+and+mycelial+growth+in+the+filamentous+fungus+Gibberella+zeae+(anamorph+Fusarium+graminearum).">The L-Type calcium ion channel Cch1 affects ascospore discharge and mycelial growth in the filamentous fungus Gibberella zeae (anamorph Fusarium graminearum).</a> Eukaryotic Cell. 7, 415-424 (2008).</li><li>Hallen, H., Huebner, M., Shiu, S. -. 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Lett. 276, 12-18 (2007).</li><li>Trail, F., Common, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Perithecial+development+by+Gibberella+zeae:+a+light+microscopy+study.">Perithecial development by Gibberella zeae: a light microscopy study.</a> Mycologia. 92, 130-138 (2000).</li><li>Trail, F., Xu, H., Loranger, R., Gadoury, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiological+and+environmental+aspects+of+ascospore+discharge+in+Gibberella+zeae+(anamorph+Fusarium+graminearum.">Physiological and environmental aspects of ascospore discharge in Gibberella zeae (anamorph Fusarium graminearum.</a> Mycologica. 94, 181-189 (2002).</li></ol>

We have nothing to disclose.

F. graminearum is particularly well adapted to the study of fruiting body development due to the availability of a well-annotated genome (<a href="http://mips.helmholtz-muenchen.de/genre/proj/FGDB/">mips.helmholtz-muenchen.de/genre/proj/FGDB/</a> ;4), and the availability of an Affymetrix-based microarray6. This has facilitated the ability to identify genes important for ascospore discharge7,11,3. The methods presented here will allow the researcher to focus on a discrete set of developmental stages and functions for genetic analysis of the fruiting bodies of F. graminearum. The methods are also easily adaptable to related fungi that can be induced to fruit in culture, and can be used as a standard for development in a variety of other fungal fruiting body types.
The ability to assess a spore firing phenotype can be subtle in species where spores are small and hard to see, such as F. graminearum. The collection of spores on a clean slide facilitates both visual assessment, and quantitative assessment, as spores may be washed off the slide and quantitated. Some fungal species produce a mucilage that surrounds their spore and the spores cannot be rinsed off, but must be counted microscopically as they remain on the slide. We have found this to be true of Sclerotinia sclerotiorum.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
		</tr>
		<tr>
			<td>Fusarium graminearum strain PH-1</td>
			<td>Fungal Genetics Stock Center, Kansas</td>
			<td>FGSC 9075</td>
		</tr>
		<tr>
			<td>Tween 60</td>
			<td>Sigma-Aldrich</td>
			<td>P1629</td>
		</tr>
		<tr>
			<td>Czapek's Dox Agar</td>
			<td>Difco, Becton Dickinson</td>
			<td>233810</td>
		</tr>
		<tr>
			<td>Potassium Chlorate</td>
			<td>Sigma-Aldrich</td>
			<td>255572</td>
		</tr>
	</tbody>
</table>

sexual development and ascospore discharge in fusarium graminearum

Fusarium graminearum has become a model system for studies in development and pathogenicity of filamentous fungi. F. graminearum most easily produces fruiting bodies, called perithecia, on carrot agar. Perithecia contain numerous tissue types, produced at specific stages of perithecium development. These include (in order of appearance) formation of the perithecium initials (which give rise to the ascogenous hyphae), the outer wall, paraphyses (sterile mycelia which occupy the center of the perithecium until the asci develop), the asci, and the ascospores within the asci14. The development of each of these tissues is separated by approximately 24 hours and has been the basis of transcriptomic studies during sexual development12,8. Refer to Hallen et al. (2007) for a more thorough description of development, including photographs of each stage. Here, we present the methods for generating and harvesting synchronously developing lawns of perithecia for temporal studies of gene regulation, development, and physiological processes. Although these methods are written specifically to be used with F. graminearum, the techniques can be used for a variety of other fungi, provided that fruiting can be induced in culture and there is some synchrony to development. We have recently adapted this protocol to study the sexual development of F. verticillioides. Although individual perithecia must be hand picked in this species, because a lawn of developing perithecia could not be induced, the process worked well for studying development (Sikhakolli and Trail, unpublished).
The most important function of fungal fruiting bodies is the dispersal of spores. In many of the species of Ascomycota (ascus producing fungi), spores are shot from the ascus, due to the generation of turgor pressure within the ascus, driving ejection of spores (and epiplasmic fluid) through the pore in the ascus tip2,7. Our studies of forcible ascospore discharge have resulted in development of a "spore discharge assay", which we use to screen for mutations in the process. Here we present the details of this assay.
F. graminearum is homothallic, and thus can form fruiting bodies in the absence of a compatible partner. The advantage of homothallism is that crossing is not necessary to generate offspring homozygous for a particular trait, a facet that has facilitated the study of sexual development in this species14,7. However, heterothallic strains have been generated that can be used for crossing5,9. It is also possible to cross homothallic strains to obtain mutants for several genes in one strain1. This is done by coinoculating one Petri dish with 2 strains. Along the meeting point, the majority of perithecia will be recombinant (provided a mutation in one of the parent strains does not inhibit outcrossing). As perithecia age, they exude ascospores en masse instead of forcibly discharging them. The resulting spore exudate (called a cirrhus) sits at the tip of the perithecium and can easily be removed for recovery of individual spores. Here we present a protocol to facilitate the identification of recombinant perithecia and the recovery of recombinant progeny.

Watch this Scientific Journal Video about Sexual Development and Ascospore Discharge in Fusarium graminearum at JoVE.com

Sexual Development and Ascospore Discharge in Fusarium graminearum

Sexual crosses and isolation of recombinant progeny are important research tools for the filamentous fungus, Fusarium graminearum, The techniques necessary successfully carry out these processes are presented.

Sexual Development and Ascospore Discharge in Fusarium graminearum

Fusarium graminearum has become a model system for studies in development and pathogenicity of filamentous fungi. F. graminearum most easily produces ...

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21.7K Views.  Michigan State University. Sexual crosses and isolation of recombinant progeny are important research tools for the filamentous fungus, Fusarium graminearum, The techniques necessary successfully carry out these processes are presented.

Video: Sexual Development and Ascospore Discharge in Fusarium graminearum

Gibberella zeae Ascospore Production and Collection for Microarray Experiments.

Fusarium graminearum Schwabe (teleomorph Gibberella zeae) is a plant pathogen causing scab disease on wheat and barley that reduces crop yield and grain quality. F. graminearum also causes stalk and ear rots of maize and is a producer of mycotoxins such as the trichothecenes that contaminate grain and are harmful to humans and livestock (Goswami and Kistler, 2004).

The fungus produces two types of spores. Ascospores, the propagules resulting from sexual reproduction, are the main source of primary infection.  These spores are forcibly discharged from mature perithecia and dispersed by wind (Francl et al 1999). Secondary infections are mainly caused by macroconidia which are produced by asexual means on the plant surface. To study the developmental processes of ascospores in this fungus, a procedure for their collection in large quantity under sterile conditions was required. Our protocol was filmed in order to generate the highest level of information for understanding and reproducibility; crucial aspects when full genome gene expression profiles are generated and interpreted. In particular, the variability of ascospore germination and biological activity are dependent on the prior manipulation of the material. The use of video for documenting every step in ascospore production is proposed in order to increase standardization, complying with the increasingly stringent requirements for microarray analysis. The procedure requires only standard laboratory equipment. Steps are shown to prevent contamination and favor time synchronization of ascospores.

To study the developmental processes of ascospores in Gibberella zeae, a procedure for collection under sterile conditions is filmed in order to generate the highest level of information for protocol description. This should facilitate the reproducibility of the experiment, a crucial aspect when full genome expression profile tests are implemented.

Fusarium graminearum Schwabe (teleomorph Gibberella zeae) is a plant pathogen causing scab disease on wheat and barley that reduces crop yield and grain ...

In vivo Bioluminescent Imaging of Mammary Tumors Using IVIS Spectrum

4T1 mouse mammary tumor cells can be implanted sub-cutaneously in nu/nu mice to form palpable tumors in 15 to 20 days. This xenograft tumor model system is valuable for the pre-clinical in vivo evaluation of putative antitumor compounds.
The 4T1 cell line has been engineered to constitutively express the firefly luciferase gene (luc2). When mice carrying 4T1-luc2 tumors are injected with Luciferin the tumors emit a visual light signal that can be monitored using a sensitive optical imaging system like the IVIS Spectrum. The photon flux from the tumor is proportional to the number of light emitting cells and the signal can be measured to monitor tumor growth and development. IVIS is calibrated to enable absolute quantitation of the bioluminescent signal and longitudinal studies can be performed over many months and over several orders of signal magnitude without compromising the quantitative result.
Tumor growth can be monitored for several days by bioluminescence before the tumor size becomes palpable or measurable by traditional physical means. This rapid monitoring can provide insight into early events in tumor development or lead to shorter experimental procedures.
Tumor cell death and necrosis due to hypoxia or drug treatment is indicated early by a reduction in the bioluminescent signal. This cell death might not be accompanied by a reduction in tumor size as measured by physical means. The ability to see early events in tumor necrosis has significant impact on the selection and development of therapeutic agents.
Quantitative imaging of tumor growth using IVIS provides precise quantitation and accelerates the experimental process to generate results.

In vivo Bioluminescent Imaging of Mammary Tumors Using IVIS Spectrum

Mammary tumor cells expressing luciferase are implanted subcutaneously in mice and visualized using optical imaging to monitor tumor growth and development non-invasively in a longitudinal study.

4T1 mouse mammary tumor cells can be implanted sub-cutaneously in nu/nu mice to form palpable tumors in 15 to 20 days. This xenograft tumor model system ...

Visualizing the Beating Heart in Drosophila

The Drosophila heart has recently emerged as a good model system for examining the genetic, cellular, and molecular mechanisms underlying function in myogenic hearts. A key step in examining heart function in the fly is finding a way to access the heart in a manner that preserves its myogenic function while still allowing the beating heart organ to be observed and recorded. Two different methods for observing and recording the beating heart in both larva and adult Drosophila are described here. Our semi-intact preparation using adult flies allows clear visualization of the abdominal heart without interference from the pigmented cuticle and overlying fat bodies. To record larval heart beats it is necessary to immobilize the larva, which minimizes body wall movements thereby reducing heart movements that are not associated with myocardial contractions. Our methodologies produce stable adult and larval heart preparations that can beat for hours at rates of 1-3 Hz.

Visualizing the Beating Heart in Drosophila

Technique required for visualizing the beating heart in larval and adult Drosophila are presented. Each life stage requires a different methodology.

The Drosophila heart has recently emerged as a good model system for examining the genetic, cellular, and molecular mechanisms underlying function in ...

Freezing and Thawing Human Embryonic Stem Cells

Since James Thomson et al developed a technique in 1998 to isolate and grow hES in culture, freezing cells for later use and thawing and expanding cells from a frozen stock have become important procedures performed in routine hES cell culture. Since hES cells are very sensitive to the stresses of freezing and thawing, special care must taken. Here we demonstrate the proper technique for rapidly thawing hES cells from liquid nitrogen stocks, plating them on mouse embryonic feeder cells, and slowly freezing them for long-term storage.

Since James Thomson et al developed a technique in 1998 to isolate and grow hES in culture, freezing cells for later use and thawing and expanding cells from a frozen stock have become important procedures performed in routine hES cell culture. Since hES cells are very sensitive to the stresses of freezing and thawing, special care must taken. Here we demonstrate the proper technique for rapidly thawing hES cells from liquid nitrogen stocks, plating them on mouse embryonic feeder cells, and slowly freezing them for long-term storage.

Since James Thomson et al developed a technique in 1998 to isolate and grow hES in culture, freezing cells for later use and thawing and expanding cells ...

Toxin Induction and Protein Extraction from Fusarium spp. Cultures for Proteomic Studies

Fusaria are filamentous fungi able to produce different toxins. Fusarium mycotoxins such as deoxynivalenol, nivalenol, T2, zearelenone, fusaric acid, moniliformin, etc... have adverse effects on both human and animal health and some are considered as pathogenicity factors. Proteomic studies showed to be effective for deciphering toxin production mechanisms (Taylor et al., 2008) as well as for identifying potential pathogenic factors (Paper et al., 2007, Houterman et al., 2007) in Fusaria. It becomes therefore fundamental to establish reliable methods for comparing between proteomic studies in order to rely on true differences found in protein expression among experiments, strains and laboratories. The procedure that will be described should contribute to an increased level of standardization of proteomic procedures by two ways. The filmed protocol is used to increase the level of details that can be described precisely. Moreover, the availability of standardized procedures to process biological replicates should guarantee a higher robustness of data, taking into account also the human factor within the technical reproducibility of the extraction procedure.
The protocol described requires 16 days for its completion: fourteen days for cultures and two days for protein extraction (figure 1). 
Briefly, Fusarium strains are grown on solid media for 4 days; they are then manually fragmented and transferred into a modified toxin inducing media (Jiao et al., 2008) for 10 days. Mycelium is collected by filtration through a Miracloth layer. Grinding is performed in a cold chamber. Different operators performed extraction replicates (n=3) in order to take into account the bias due to technical variations (figure 2). Extraction was based on a SDS/DTT buffer as described in Taylor et al. (2008) with slight modifications. Total protein extraction required a precipitation process of the proteins using Aceton/TCA/DTT buffer overnight and Acetone /DTT washing (figure 3a,3b). Proteins were finally resolubilized in the protein-labelling buffer and quantified. Results of the extraction were visualized on a 1D gel (Figure 4, SDS-PAGE), before proceeding to 2D gels (IEF/SDS-PAGE). The same procedure can be applied for proteomic analyses on other growing media and other filamentous fungi (Miles et al., 2007).

Toxin Induction and Protein Extraction from Fusarium spp. Cultures for Proteomic Studies

Protein extraction for proteomic analyses in fungal species requires high levels of standardization to be accomplished according with the minimum information about a proteomic experiment (MIAPE) guidelines. We present a video-protocol that includes a procedure for minimizing experimental bias during toxin induction and protein extraction from Fusarium spp.

Fusaria are filamentous fungi able to produce different toxins. Fusarium mycotoxins such as deoxynivalenol, nivalenol, T2, zearelenone, fusaric acid, ...

Evaluation of Mammary Gland Development and Function in Mouse Models

The human mammary gland is composed of 15-20 lobes that secrete milk into a branching duct system opening at the nipple. Those lobes are themselves composed of a number of terminal duct lobular units made of secretory alveoli and converging ducts1. In mice, a similar architecture is observed at pregnancy in which ducts and alveoli are interspersed within the connective tissue stroma. The mouse mammary gland epithelium is a tree like system of ducts composed of two layers of cells, an inner layer of luminal cells surrounded by an outer layer of myoepithelial cells denoted by the confines of a basement membrane2. At birth, only a rudimental ductal tree is present, composed of a primary duct and 15-20 branches. Branch elongation and amplification start at the beginning of puberty, around 4 weeks old, under the influence of hormones3,4,5. At 10 weeks, most of the stroma is invaded by a complex system of ducts that will undergo cycles of branching and regression in each estrous cycle until pregnancy2. At the onset of pregnancy, a second phase of development begins, with the proliferation and differentiation of the epithelium to form grape-shaped milk secretory structures called alveoli6,7. Following parturition and throughout lactation, milk is produced by luminal secretory cells and stored within the lumen of alveoli. Oxytocin release, stimulated by a neural reflex induced by suckling of pups, induces synchronized contractions of the myoepithelial cells around the alveoli and along the ducts, allowing milk to be transported through the ducts to the nipple where it becomes available to the pups 8. Mammary gland development, differentiation and function are tightly orchestrated and require, not only interactions between the stroma and the epithelium, but also between myoepithelial and luminal cells within the epithelium9,10,11. Thereby, mutations in many genes implicated in these interactions may impair either ductal elongation during puberty or alveoli formation during early pregnancy, differentiation during late pregnancy and secretory activation leading to lactation12,13. In this article, we describe how to dissect mouse mammary glands and assess their development using whole mounts. We also demonstrate how to evaluate myoepithelial contractions and milk ejection using an ex-vivo oxytocin-based functional assay. The effect of a gene mutation on mammary gland development and function can thus be determined in situ by performing these two techniques in mutant and wild-type control mice.

This method describes how to dissect and assess mammary gland development and function from mice. Excised mammary glands are assessed for the degree of development using whole mount while milk ejection is evaluated using an oxytocin-based myoepithelial cell contraction assay.

The human mammary gland is composed of 15-20 lobes that secrete milk into a branching duct system opening at the nipple. Those lobes are themselves ...

Combined DNA-RNA Fluorescent In situ Hybridization (FISH) to Study X Chromosome Inactivation in Differentiated Female Mouse Embryonic Stem Cells

Fluorescent in situ hybridization (FISH) is a molecular technique which enables the detection of nucleic acids in cells. DNA FISH is often used in cytogenetics and cancer diagnostics, and can detect aberrations of the genome, which often has important clinical implications. RNA FISH can be used to detect RNA molecules in cells and has provided important insights in regulation of gene expression. Combining DNA and RNA FISH within the same cell is technically challenging, as conditions suitable for DNA FISH might be too harsh for fragile, single stranded RNA molecules. We here present an easily applicable protocol which enables the combined, simultaneous detection of Xist RNA and DNA encoded by the X chromosomes. This combined DNA-RNA FISH protocol can likely be applied to other systems where both RNA and DNA need to be detected.

Combined DNA-RNA Fluorescent In situ Hybridization FISH to Study X Chromosome Inactivation in Differentiated Female Mouse Embryonic Stem Cells

Fluorescent in situ hybridization (FISH) allows the detection of nucleic acids in their native environment within cells. We here describe a protocol for the combined, simultaneous detection of RNA and DNA by means of FISH, which can be used to study X chromosome inactivation in mouse embryonic stem cells.

Fluorescent in situ hybridization (FISH) is a molecular technique which enables the detection of nucleic acids in cells. DNA FISH is often used in ...

Microscopy of Fission Yeast Sexual Lifecycle

The fission yeast Schizosaccharomyces pombe has been an invaluable model system in studying the regulation of the mitotic cell cycle progression, the mechanics of cell division and cell polarity. Furthermore, classical experiments on its sexual reproduction have yielded results pivotal to current understanding of DNA recombination and meiosis. More recent analysis of fission yeast mating has raised interesting questions on extrinsic stimuli response mechanisms, polarized cell growth and cell-cell fusion. To study these topics in detail we have developed a simple protocol for microscopy of the entire sexual lifecycle. The method described here is easily adjusted to study specific mating stages. Briefly, after being grown to exponential phase in a nitrogen-rich medium, cell cultures are shifted to a nitrogen-deprived medium for periods of time suited to the stage of the sexual lifecycle that will be explored. Cells are then mounted on custom, easily built agarose pad chambers for imaging. This approach allows cells to be monitored from the onset of mating to the final formation of spores.

We provide a reproducible basic method for the long-term microscopy of the fission yeast sexual lifecycle. With minor adjustments described, the presented protocol allows research focus on different steps of the reproductive process.

The fission yeast Schizosaccharomyces pombe has been an invaluable model system in studying the regulation of the mitotic cell cycle progression, the ...

Gap Junctional Intercellular Communication: A Functional Biomarker to Assess Adverse Effects of Toxicants and Toxins, and Health Benefits of Natural Products

This protocol describes a scalpel loading-fluorescent dye transfer (SL-DT) technique that measures intercellular communication through gap junction channels, which is a major intercellular process by which tissue homeostasis is maintained. Interruption of gap junctional intercellular communication (GJIC) by toxicants, toxins, drugs, etc. has been linked to numerous adverse health effects. Many genetic-based human diseases have been linked to mutations in gap junction genes. The SL-DT technique is a simple functional assay for the simultaneous assessment of GJIC in a large population of cells. The assay involves pre-loading cells with a fluorescent dye by briefly perturbing the cell membrane with a scalpel blade through a population of cells. The fluorescent dye is then allowed to traverse through gap junction channels to neighboring cells for a designated time. The assay is then terminated by the addition of formalin to the cells. The spread of the fluorescent dye through a population of cells is assessed with an epifluorescence microscope and the images are analyzed with any number of morphometric software packages that are available, including free software packages found on the public domain. This assay has also been adapted for in vivo studies using tissue slices from various organs from treated animals. Overall, the SL-DT assay can serve a broad range of in vitro pharmacological and toxicological needs, and can be potentially adapted for high throughput set-up systems with automated fluorescence microscopy imaging and analysis to elucidate more samples in a shorter time.

This protocol describes a scalpel loading-fluorescent dye transfer technique that measures intercellular communication through gap junction channels. Gap junctional intercellular communication is a major cellular process by which tissue homeostasis is maintained and disruption of this cell signaling has adverse health effects.

This protocol describes a scalpel loading-fluorescent dye transfer (SL-DT) technique that measures intercellular communication through gap junction ...

G Protein-selective GPCR Conformations Measured Using FRET Sensors in a Live Cell Suspension Fluorometer Assay

F&#1255;rster resonance energy transfer (FRET)-based studies have become increasingly common in the investigation of GPCR signaling. Our research group developed an intra-molecular FRET sensor to detect the interaction between G&#945; subunits and GPCRs in live cells following agonist stimulation. Here, we detail the protocol for detecting changes in FRET between the &#946;2-adrenergic receptor and the G&#945;s C-terminus peptide upon treatment with 100 &#181;M isoproterenol hydrochloride as previously characterized1. Our FRET sensor is a single polypeptide consisting serially of a full-length GPCR, a FRET acceptor fluorophore (mCitrine), an ER/K SPASM (systematic protein affinity strength modulation) linker, a FRET donor fluorophore (mCerulean), and a G&#945; C-terminal peptide. This protocol will detail cell preparation, transfection conditions, equipment setup, assay execution, and data analysis. This experimental design detects small changes in FRET indicative of protein-protein interactions, and can also be used to compare the strength of interaction across ligands and GPCR-G protein pairings. To enhance the signal-to-noise in our measurements, this protocol requires heightened precision in all steps, and is presented here to enable reproducible execution.

Simple methods to detect the selective activation of G proteins by G protein-coupled receptors remain an outstanding challenge in cell signaling. Here, F&#1255;rster resonance energy transfer (FRET) biosensors have been developed by pairwise tethering a GPCR to G protein peptides to probe conformational changes at controlled concentrations in live cells.

F&#1255;rster resonance energy transfer (FRET)-based studies have become increasingly common in the investigation of GPCR signaling. Our research group ...