Name: analysis of epididymal protein synthesis and secretion
Uploaded: 2018-08-25T15:00:00
Description: Watch this Scientific Journal Video about Analysis of Epididymal Protein Synthesis and Secretion at JoVE.com

The authors would like to acknowledge the National Health and Medical Research Council of Australia Project Grant APP1103176 for the support of this work.

All experimental procedures involving animal tissue collection were approved by the University of Newcastle&#39;s Animal Care and Ethics Committee.
1. Immunofluorescence Staining of the Paraffin-embedded Epididymal Sections (Figures 1 and 2)
<ol>
	<li>Immediately after the euthanasia of adult mice via CO2 inhalation (Swiss mice, over 8 weeks old), carefully dissect the epididymis (using surgical scissors and tweezers) free of overlying connective tissue and fat and immerse in Boui...

These studies incorporated the use of Bouin&#39;s fixed epididymal tissue that had been subjected to paraffin embedding and standard sectioning protocols. Bouin&#39;s fixative solution comprises a mixture of formaldehyde, picric acid and acetic acid, with each component having a specific and complementary function. Thus, formaldehyde reacts with primary amines to form protein cross-links, picric acid slowly penetrates the tissue forming salts and hence coagulation of basic proteins and conversely, acetic acid rapidly pen...

The spermatozoa of all mammalian species acquire the potential to display forward progressive motility and to fertilize an ovum during their prolonged descent through the epididymis, a highly specialized region of the male extra-testicular duct system, which may take 7 - 14 days to navigate (depending on the species)1. Due to the extreme condensation of the paternal chromatin and the shedding of the majority of cytoplasm that accompanies the cytodifferentiation of spermatozoa within the testes, their subsequent functional maturation is driven exclusively by their interaction with the epididymal microenvironment. This milieu is, in turn, created by the secretory and absorptive activity of the lining epididymal soma and displays an exceptional level of segment-segment variation1. Thus, the most active segments in terms of protein synthesis and secretion are those located in the proximal portion of the epididymis (namely, the caput and corpus)2. This activity mirrors the functional profile of spermatozoa, with the cells first beginning to display hallmarks of functional competence (i.e., progressive motility and the ability to bind to acid-solubilized zona glycoproteins) following their passage through the caput epididymis3. These functional attributes continue to develop before reaching optimal levels as the sperm reach the distal epididymal segment (cauda), wherein they are stored in a quiescent state in readiness for ejaculation. The formation and maintenance of this sperm storage reservoir is also intimately tied to the lining epithelium, which in the cauda is dominated by strong absorptive activity4,5. Although anatomical differences have been reported6,7,8, such regionalized division of labor appears to be a characteristic of the epididymis that is shared among the majority of mammalian species studied to date, including our own9,10. Indeed, from a clinical perspective, it is known that epididymal dysfunction makes an important contribution to the etiology of male factor infertility11, thus highlighting the importance of understanding the regulation of this specialized tissue.
It is therefore regrettable that our understanding of epididymal physiology, and the mechanisms that regulate the sequential phases of sperm maturation and storage within this tissue, remain to be fully resolved. Among the contributing factors, limiting advances in epididymal research are the overall complexity of this tissue and knowledge of the mechanisms that exert regulatory control over its luminal microenvironment. Anatomically, we know that beyond the distinction of caput, corpus and cauda segments, the epididymis can be further subdivided into several zones (Figure 1A), each separated by septa12 and characterized by discrete profiles of gene/protein expression13,14,15,16,17,18. Indeed, on the basis of detailed transcriptional profiling of segmental gene expression in the epididymis, as many as 6 and 9 distinct epididymal zones have been reported in the mouse and rat models, respectively19,20. Such complexity presumably reflects the composition of the epididymal soma, a pseudostratified epithelium comprising numerous different cell types; each differing with respect to their abundance, distribution and secretory/absorptive activities along the length of the tract. Thus, principal cells are by far the most abundant epididymal cell type constituting upwards of 80% of all epithelial cells. Accordingly, principal cells are responsible for the bulk of epididymal protein biosynthesis and secretion5. In contrast, the clear cell population, which rank as the second most abundant cell type within the epididymal soma, are primarily involved in selective absorption of luminal components and the acidification of this microenvironment5. Adding another tier of complexity, androgens and other lumicrine factors of testicular origin exert differential control over each of these epididymal cell types depending on their positioning along the tract.
Despite the limitations imposed by such complexity, significant inroads continue to be made into resolving the mechanistic basis of epididymal function. A key to these studies has been the application of advanced mass spectrometry strategies to establish broad scale inventories of the epididymal proteome, in tandem with detailed analyses of individual proteins selected from among these initial surveys. An illustration of this approach is our recent characterization of the DNM family of mechanoenzymes in the mouse model21. Our initial interest in DNM was fueled by its dual action in the coupling of exo- and endocytotic processes. Building on these observations, we were able to demonstrate that the three canonical isoforms of DNM (DNM1 - DNM3) are highly expressed in the mouse epididymis and appropriately positioned to fulfill regulatory roles in protein secretion and absorption21. Moreover, we were able to clearly differentiate each DNM isoform on the basis of their cellular and sub-cellular localization, thus suggesting that they possess complementary, as opposed to redundant, activity within the epididymal epithelium21.
Here, we describe the experimental methodology employed for the study of DNM expression in the mouse epididymis with the hope that this information will find wider application in the characterization of alternative epididymal proteins and thus contribute to our understanding of the function of this important element of the male reproductive tract. Specifically, we describe the development of robust methodology for immunofluorescence labeling of target proteins in paraffin-embedded epididymal sections and the subsequent detection of the spatial distribution of these proteins via immunofluorescence microscopy. We further document our recently optimized protocols22 for the isolation and characterization of epididymosomes; small exosome-like vesicles that constitute key elements of the epididymal secretory profile and appear to hold a prominent role in promoting sperm maturation23. As a complementary approach, we also describe the immunofluorescence detection of target proteins in an immortalized mouse caput epididymal epithelial (mECap18) cell line and the use of this resource as a model with which to explore the regulation of epididymal secretory activity in vitro.

<table>
	<tbody>
		<tr>
			<td>Dynamin 1 antibody</td>
			<td>Abcam</td>
			<td>ab108458</td>
			<td>Host species: Rabbit, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Dynamin 2 antibody</td>
			<td>Santa Cruz</td>
			<td>sc-6400</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Dynamin 3 antibody</td>
			<td>Proteintech</td>
			<td>14737-1-AP</td>
			<td>Host species: Rabbit, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>ATP6V1B1 antibody</td>
			<td>Santa Cruz</td>
			<td>sc-21206</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>CD9 antibody</td>
			<td>BD Pharmingen</td>
			<td>553758</td>
			<td>Host species: Rat, Isotype: IgG, Class: monoclonal</td>
		</tr>
		<tr>
			<td>Flotillin-1 antibody</td>
			<td>Sigma</td>
			<td>F1180</td>
			<td>Host species: Rabbit, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>ALOX15 antibody</td>
			<td>Abcam</td>
			<td>ab80221</td>
			<td>Host species: Rabbit, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>TUBB antibody</td>
			<td>Santa Cruz</td>
			<td>sc-5274</td>
			<td>Host species: Mouse, Isotype: IgG, Class: monoclonal</td>
		</tr>
		<tr>
			<td>PSMD7 antibody</td>
			<td>Abcam</td>
			<td>ab11436</td>
			<td>Host species: Rabbit, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Rabbit Alexa Fluor 488</td>
			<td>Thermo</td>
			<td>A11008</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Goat Alexa Fluor 488</td>
			<td>Thermo</td>
			<td>A11055</td>
			<td>Host species: Donkey, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Goat Alexa Fluor 594</td>
			<td>Thermo</td>
			<td>A11058</td>
			<td>Host species: Donkey, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Rat Alexa Fluor 594</td>
			<td>Thermo</td>
			<td>A11007</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Rabbit HRP</td>
			<td>Millipore</td>
			<td>DC03L</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Rat HRP</td>
			<td>Millipore</td>
			<td>DC01L</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>Anti Mouse HRP</td>
			<td>Santa Cruz</td>
			<td>sc-2005</td>
			<td>Host species: Goat, Isotype: IgG, Class: polyclonal</td>
		</tr>
		<tr>
			<td>4&#39;, 6-diamidino-2-phenylindole (DAPI)</td>
			<td>Sigma</td>
			<td>D9564</td>
			<td></td>
		</tr>
		<tr>
			<td>propidium iodide (PI)</td>
			<td>Sigma</td>
			<td>P4170</td>
			<td></td>
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		<tr>
			<td>Mowiol 4-88</td>
			<td>Calbiochem</td>
			<td>475904</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA)</td>
			<td>Sigma</td>
			<td>A7906</td>
			<td></td>
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		<tr>
			<td>fetal bovine serum (FBS)</td>
			<td>Bovogen</td>
			<td>SFBS-F</td>
			<td></td>
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		<tr>
			<td>DMEM</td>
			<td>Thermo</td>
			<td>11960-044</td>
			<td></td>
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		<tr>
			<td>L-glutamine</td>
			<td>Thermo</td>
			<td>25030-081</td>
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		<tr>
			<td>penicillin/streptomycin</td>
			<td>Thermo</td>
			<td>15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>5&#945;-androstan-17&#946;-ol-3-oneC-IIIN</td>
			<td>Sigma</td>
			<td>A8380</td>
			<td></td>
		</tr>
		<tr>
			<td>sodium pyruvate</td>
			<td>Thermo</td>
			<td>11360-070</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-ethylenediaminetetraacetic acid (EDTA)</td>
			<td>Sigma</td>
			<td>T4049</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraformaldehyde (PFA)</td>
			<td>EMS</td>
			<td>15710</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylene</td>
			<td>VWR Chemicals</td>
			<td>1330-20-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>VWR Chemicals</td>
			<td>64-17-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline (PBS)</td>
			<td>Sigma</td>
			<td>P4417</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium citrate</td>
			<td>Sigma</td>
			<td>S1804</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>Astral</td>
			<td>0497-5KG</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma</td>
			<td>G5516</td>
			<td></td>
		</tr>
		<tr>
			<td>1, 4-diazabicyclo-(2.2.2)-octane</td>
			<td>Sigma</td>
			<td>D2522</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-gysine</td>
			<td>Sigma</td>
			<td>P4832</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>78787</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue</td>
			<td>Sigma</td>
			<td>T6146</td>
			<td></td>
		</tr>
		<tr>
			<td>Trichloroacetic acid</td>
			<td>Sigma</td>
			<td>T9159</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>Ajax Finechem</td>
			<td>A6-2.5 L GL</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Sigma</td>
			<td>S0389</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly (vinyl alcohol)</td>
			<td>Sigma</td>
			<td>P8136</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Glucose</td>
			<td>Ajax Finechem</td>
			<td>783-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>OptiPrep Density Gradient Medium</td>
			<td>Sigma</td>
			<td>D1556</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence microscopy</td>
			<td>Zeiss</td>
			<td>Zeiss Axio Imager A1</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultracentrifuge</td>
			<td>BECKMAN COULTER</td>
			<td>Optima Max-XP</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuges</td>
			<td>Eppendorf</td>
			<td>5424R</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Heracell</td>
			<td>150</td>
			<td></td>
		</tr>
		<tr>
			<td>Large Orbital Shaker</td>
			<td>Ratek</td>
			<td>OM7</td>
			<td></td>
		</tr>
		<tr>
			<td>Microwave</td>
			<td>LG</td>
			<td>MS3840SR /00</td>
			<td></td>
		</tr>
		<tr>
			<td>Lab pH Meter</td>
			<td>MeterLab</td>
			<td>PHM220</td>
			<td></td>
		</tr>
		<tr>
			<td>Liquid-repellent slide marker</td>
			<td>Daido Sangyo</td>
			<td>Mini</td>
			<td></td>
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		<tr>
			<td>Coverslip</td>
			<td>Thermo</td>
			<td>586</td>
			<td></td>
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		<tr>
			<td>6 well plate</td>
			<td>CELLSTAR</td>
			<td>657160</td>
			<td></td>
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		<tr>
			<td>12 well plate</td>
			<td>CELLSTAR</td>
			<td>665180</td>
			<td></td>
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		<tr>
			<td>Slide</td>
			<td>Mikro-Glass</td>
			<td>SF41296PLMK</td>
			<td></td>
		</tr>
		<tr>
			<td>0.45 &#181;m filter</td>
			<td>Millox-HV</td>
			<td>SLHV033RS</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes Dustfree Paper</td>
			<td>KIMTECH</td>
			<td>34155</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultracentrifuge tube (2.2 ml, 11 &#215; 35 mm)</td>
			<td>BECKMAN COULTER</td>
			<td>347356</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultracentrifuge tube (3.2 ml, 13 &#215; 56 mm)</td>
			<td>BECKMAN COULTER</td>
			<td>362305</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell strainer 70 &#181;m Nylon</td>
			<td>FALCON</td>
			<td>352350</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish 35 &#215; 10 mm with cams</td>
			<td>SARSTED</td>
			<td>82.1135.500</td>
			<td></td>
		</tr>
		<tr>
			<td>Slide jar</td>
			<td>TRAJAN</td>
			<td>#23 319 00</td>
			<td></td>
		</tr>
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</table>

analysis of epididymal protein synthesis and secretion

The mammalian epididymis generates one of the most complex intraluminal fluids of any endocrine gland in order to support the post-testicular maturation and storage of spermatozoa. Such complexity arises due to the combined secretory and absorptive activity of the lining epithelial cells. Here, we describe the techniques for the analysis of epididymal protein synthesis and secretion by focusing on the model protein family of dynamin (DNM) mechanoenzymes; large GTPases that have the potential to regulate bi-directional membrane trafficking events. For the study of protein expression in epididymal tissue, we describe robust methodology for immunofluorescence labeling of target proteins in paraffin-embedded sections and the subsequent detection of the spatial distribution of these proteins via immunofluorescence microscopy. We also describe optimized methodology for the isolation and characterization of exosome like vesicles, known as epididymosomes, which are secreted into the epididymal lumen to participate in intercellular communication with maturing sperm cells. As a complementary approach, we also describe the immunofluorescence detection of target proteins in an SV40-immortalized mouse caput epididymal epithelial (mECap18) cell line. Moreover, we discuss the utility of the mECap18 cell line as a suitable in vitro model with which to explore the regulation of epididymal secretory activity. For this purpose, we describe the culturing requirements for the maintenance of the mECap18 cell line and the use of selective pharmacological inhibition regimens that are capable of influencing their secretory protein profile. The latter are readily assessed via harvesting of conditioned culture medium, concentration of secreted proteins via trichloroacetic acid/acetone precipitation and their subsequent analysis via SDS-PAGE and immunoblotting. We contend that these combined methods are suitable for the analysis of alternative epididymal protein targets as a prelude to determining their functional role in sperm maturation and/or storage.

Figure 1 and Figure 2 show representative results of immunofluorescence localization of DNM in the mouse caput epididymis. Each of the three DNM isoforms investigated display distinct localization profiles. Thus, DNM1 is characterized by relatively modest diffuse labeling of the epididymal cells throughout the initial segment and caput epididymis (Figure 2A). By contrast, the DNM2 is...

Watch this Scientific Journal Video about Analysis of Epididymal Protein Synthesis and Secretion at JoVE.com

Analysis of Epididymal Protein Synthesis and Secretion

Here, we report the immunofluorescence localization of dynamin to illustrate the protocols for the detection of proteins in paraffin-embedded mouse epididymal sections and those of an immortalized epididymal cell line (mECap18). We also describe the protocols for the isolation of secretory proteins from both epididymal fluid and conditioned cell media.

The mammalian epididymis generates one of the most complex intraluminal fluids of any endocrine gland in order to support the post-testicular maturation ...

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