Name: fabricating complex culture substrates using robotic microcontact printing (r-&#181;cp) and sequential nucleophilic substitution
Uploaded: 2014-10-31T15:00:00
Description: Watch this Scientific Journal Video about Fabricating Complex Culture Substrates Using Robotic Microcontact Printing R-Ã‚ÂµCP and Sequential Nucleophilic Substitution at JoVE.com

Funding for this work, GTK, TK, and JDM were provided by the Wisconsin Institute for Discovery and the Wisconsin Alumni Research Foundation.

1. Generating Elastomeric Stamps
<ol style="margin-left: 40px;">
	<li>To generate the PDMS stamp&#8217;s silicon masters, design the photomask&#8217;s feature patterns using computer-aided design software.
	<ol>
		<li>Design the first pattern as a 20 x 20 array of annuli with 300 &#956;m inner diameter (ID) and 600 &#956;m OD with 1,200 &#956;m center-to-center spacing.</li>
		<li>Design the second pattern as a 20 x 20 array of annuli with 600 &#956;m ID and 900 &#956;m OD with 1,200 &#956;m center-to-center spacing.</...

<ol>
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M., Chilkoti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simple+Fabrication+of+Antibody+Microarrays+on+Nonfouling+Polymer+Brushes+with+Femtomolar+Sensitivity+for+Protein+Analytes+in+Serum+and+Blood.">Simple Fabrication of Antibody Microarrays on Nonfouling Polymer Brushes with Femtomolar Sensitivity for Protein Analytes in Serum and Blood.</a> Advanced Materials. 21 (19), 1968-1971 (2009).</li><li>Hucknall, A., Rangarajan, S., Chilkoti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+Pursuit+of+Zero:+Polymer+Brushes+that+Resist+the+Adsorption+of+Proteins.">In Pursuit of Zero: Polymer Brushes that Resist the Adsorption of Proteins.</a> Advanced Materials. 21 (23), 2441-2446 (2009).</li><li>Rozkiewicz, D. I., Ja&#324;czewski, D., Verboom, W., Ravoo, B. J., Reinhoudt, D. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Click&#8221;+Chemistry+by+Microcontact+Printing.">Click&#8221; Chemistry by Microcontact Printing.</a> Angewandte Chemie International Edition. 45 (32), 5292-5296 (2006).</li><li>Jewett, J. C., Bertozzi, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cu-free+click+cycloaddition+reactions+in+chemical+biology.">Cu-free click cycloaddition reactions in chemical biology.</a> Chemical Society Reviews. 39 (4), 1272-1279 (2010).</li><li>Sha, J., Lippmann, E. S., McNulty, J., Ma, Y., Ashton, R. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sequential+Nucleophilic+Substitutions+Permit+Orthogonal+Click+Functionalization+of+Multicomponent+PEG+Brushes.">Sequential Nucleophilic Substitutions Permit Orthogonal Click Functionalization of Multicomponent PEG Brushes.</a> Biomacromolecules. 14 (9), 3294-3303 (2013).</li><li>Tugulu, S., Silacci, P., Stergiopulos, N., Klok, H. -. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RGD&#8212;Functionalized+polymer+brushes+as+substrates+for+the+integrin+specific+adhesion+of+human+umbilical+vein+endothelial+cells.">RGD&#8212;Functionalized polymer brushes as substrates for the integrin specific adhesion of human umbilical vein endothelial cells.</a> Biomaterials. 28 (16), 2536-2546 (2007).</li><li>Ashton, R. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-Throughput+Screening+of+Gene+Function+in+Stem+Cells+Using+Clonal+Microarrays.">High-Throughput Screening of Gene Function in Stem Cells Using Clonal Microarrays.</a> Stem Cells. 25 (11), 2928-2935 (2007).</li><li>Koepsel, J. T., Murphy, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterned+Self-Assembled+Monolayers:+Efficient,+Chemically+Defined+Tools+for+Cell+Biology.">Patterned Self-Assembled Monolayers: Efficient, Chemically Defined Tools for Cell Biology.</a> ChemBioChem. 13 (12), 1717-1724 (2012).</li><li>Mrksich, M., Dike, L. E., Tien, J., Ingber, D. E., Whitesides, G. 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C., Cabrera, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+instrument+for+automated+microcontact+printing+with+stamp+load+adjustment.">A new instrument for automated microcontact printing with stamp load adjustment.</a> Review of Scientific Instruments. 79 (6), (2008).</li><li>Trinkle, C. A., Lee, L. 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P., Chilkoti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface-Initiated+Atom+Transfer+Radical+Polymerization+of+Oligo(ethylene+glycol)+Methyl+Methacrylate+from+a+Mixed+Self-Assembled+Monolayer+on+Gold.">Surface-Initiated Atom Transfer Radical Polymerization of Oligo(ethylene glycol) Methyl Methacrylate from a Mixed Self-Assembled Monolayer on Gold.</a> Advanced Functional Materials. 16 (5), 640-648 (2006).</li><li>Scadden, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+stem-cell+niche+as+an+entity+of+action.">The stem-cell niche as an entity of action.</a> Nature. 441 (7097), (2006).</li><li>Codelli, J. A., Baskin, J. M., Agard, N. J., Bertozzi, C. 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Ideal substrates for tissue engineering would be bioinspired and thereby recapitulate the spatial distribution of critical bioactive ligands found within the native tissues. They would also possess dynamic properties that enable temporal adjustments of the ligands and the spatial patterns in which they are presented to permit directed tissue morphogenesis and spatially restricted induction of cell fate. Fabrication of such substrates requires the immobilization of multiple biochemical cues in complex and highly ordered o...

The ability of PEG-grafted surfaces to display covalently bound biochemical ligands while simultaneously maintaining inherent non-fouling properties make them an ideal choice for engineering custom microscale environments on culture substrates1,2,3. The biospecific interactions mediated by ligand conjugated PEG brushes enables reductionistic analysis of the effects of biochemical cues found within complex in vivo tissue microenvironments on individual cell phenotypes. Furthermore, bio-orthogonal &#8220;click&#8221; chemistries can be used to facilitate directional immobilization of ligands so that they are presented in native conformations4-6. Thus, microscale spatial patterning of PEG brushes is a versatile tool to create designer in vitro niches to investigate cell signaling induced by immobilized biochemical cues6,7.
A common method for generating spatial patterns of biochemical cues entails microcontact printing (&#956;CP) gold-coated substrates with patterns of PEG conjugated alkanethiols. Then, the micropatterned self-assembled monolayers (SAMs) of PEG-ylated alkanethiols restricts physical adsorption of biochemical molecules, e.g., proteins, only to non-patterned regions of the substrate8,9. However, the SAMs generated by this technique are sensitive to oxidation in long term cell culture media. Thus, &#956;CP&#8217;d alkanethiol SAMs are often further grafted with PEG polymer brushes using surface-initiated atom transfer radical polymerization (SI-ATRP) to increase the region&#8217;s non-fouling stability10. Specifically, &#956;CP of the alkanethiol polymerization initiator, &#969;-meraptoundecyl bromoisobutyrate, on gold-coated surfaces followed by SI-ATRP of poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) monomers generates surfaces with micropatterned long-term, stable, and non-fouling PEG brushes. Moreover, these are capable of being further modified to present diverse chemical moieties11.
Taking advantage of this property, Sha et. al. developed a method to engineer culture substrates with multicomponent PEGMEMA brushes presenting orthogonal &#8220;click&#8221; chemistries. In this method, they use a series of &#956;CP/SI-ATRP steps interspersed with sequential sodium azide, ethanolamine, and propargylamine nucleophilic substitutions to create culture substrates presenting microscale patterns of multiple immobilized ligands6. While the potential of using such chemistries in conjunction with manual &#956;CP to engineer novel culture substrates is immense, it is limited by the precision and accuracy with which multiple &#956;CP steps can be aligned on a single substrate. A high level of precision and accuracy would be required to reproducibly manufacture complex in vitro niches using these versatile techniques.
To address this limitation, several automated and semi-automated &#956;CP systems have been generated. Chakra et. al. developed a &#956;CP system in which custom stamps are placed on a rail system and brought into conformal contact with gold-coated slides using a computer-controlled pneumatic actuator. However, this method requires the precise fabrication of custom stamp designs and reports a 10 &#956;m precision with no report of the accuracy achieved when performing multiple &#956;CP steps12. More recently, a method utilizing an integrated kinematic coupling system reported precision below 1 &#956;m using a single pattern, but were unable to accurately align multiple patterns due to a lack of precise control of stamp features from mold to mold13. Additionally, both of the previous methods require the substrate to remain fixed between patterning steps, thereby significantly limiting the diversity of surface modification chemistries that can be utilized. Here, we describe an automated R-&#956;CP system capable of accurate and precise alignment of multiple &#956;CP steps while allowing maximal flexibility in stamp design and fabrication. Furthermore, the patterned substrates can be repeatedly removed from the system between stampings, thereby permitting the use of diverse substrate modification chemistries, including sequential nucleophilic substitutions. Substrates engineered using such chemistries have been used for cell culture previously by both us6,14 and others7. Thus, we have merged R-&#956;CP and sequential nucleophilic substitution reactions to develop a method for scalable manufacture of culture substrates with complex and micropatterned biochemical cues.

<table border="0" cellpadding="0" cellspacing="0" width="740">
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			<td height="21" style="height:21px;width:185px;">Name</td>
			<td style="width:185px;">Company</td>
			<td style="width:185px;">Catalog Number</td>
			<td style="width:185px;">Comments</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:185px;">SCARA&#160;</td>
			<td style="width:185px;">Epson</td>
			<td style="width:185px;">LS3-401ST</td>
			<td style="width:185px;">Higher end models with increased precision are available if desired.&#160;</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:185px;">(TRIDECAFLUORO-1,1,2,2-TETRAHYDROOCTYL)TRICHLOROSILANE</td>
			<td style="width:185px;">Gelest</td>
			<td style="width:185px;">SIT8174.0</td>
			<td style="width:185px;">CAUTION, Should only be handled in a chemical fume hood. When silanizing wafers no one should enter the hood until all silane has been evaporated.</td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:185px;">Sylgard 184 Silicone Elastomer Kit</td>
			<td style="width:185px;">Ellsworth Adhesive Co</td>
			<td style="width:185px;">NC9020938</td>
			<td style="width:185px;">Thouroughly degass solutions via vacuum exposure before use. Alternative kits such as Kit 182 are acceptable.</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:185px;">24mm X 50 mm #1 Cover Glass Slides</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td style="width:185px;">48393106</td>
			<td style="width:185px;">These can be purchased from a number of suppliers with varying dimensions to suit need.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">CHA-600 Telemark Electron Beam Evaporator</td>
			<td style="width:185px;">Telemark</td>
			<td style="width:185px;">SEC-600-RAP</td>
			<td style="width:185px;">Requries specialized training.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:185px;">EPSON LS3 SCARA</td>
			<td style="width:185px;">EPSON</td>
			<td style="width:185px;">LS3-401ST</td>
			<td style="width:185px;"></td>
		</tr>
		<tr height="105">
			<td height="105" style="height:105px;width:185px;">&#969;-mertcaptoundecyl bromoisobutyrate</td>
			<td style="width:185px;">Prochimia</td>
			<td style="width:185px;">FT 015-m11-0.2</td>
			<td style="width:185px;">Store at -20&#176;C. Other ATRP initiators may be used as this R-&#956;CP platform is applicable to all micropatterning modalities.&#160;</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Schlenk Tube Flask 50 mL</td>
			<td style="width:185px;">Synthware</td>
			<td style="width:185px;">60003-078</td>
			<td style="width:185px;">Requires rubber stoppers with diaphram.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:185px;">Poly(ethylene glycol) methyl ether methacrylate</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">447943</td>
			<td style="width:185px;">Shipped containing MEHQ and BHT free readical inhibitors.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Methanol (Certified ACS)</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td style="width:185px;">A412-4</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Copper(II) Bromide</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">437867</td>
			<td style="width:185px;">CAUTION, limit exposure with surgical mask.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">2&#39;,2-Bipyridine</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">D216305</td>
			<td style="width:185px;">CAUTION, limit exposure with surgical mask.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:185px;">Sodium L-Ascorbate</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">A4034</td>
			<td style="width:185px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">20mL Borosilicate Glass Scintillation Vials</td>
			<td style="width:185px;">Fisher Scientific</td>
			<td style="width:185px;">03-340-4E</td>
			<td style="width:185px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Sodium Azide</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">S2002</td>
			<td style="width:185px;">CAUTION, limit exposure with surgical mask.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">N,N-dimethyformamide</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">227056</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Ethanolamine</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">398136</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Triethylamine</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">T0886</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Dimethylsulfoxide</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">276855</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Propargylamine</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">P50900</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:185px;">200 Proof Ethanol</td>
			<td style="width:185px;">University of Wisconsin Material Distribution Services</td>
			<td style="width:185px;">2292</td>
			<td style="width:185px;">CAUTION, only handle in chemical fume hood.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:185px;">Azide-PEG3-Biotin</td>
			<td style="width:185px;">ClickChemistryTools</td>
			<td style="width:185px;">AZ104-100</td>
			<td style="width:185px;">Solubilized in DMF</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Copper(II) Sulfate</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">C1297</td>
			<td style="width:185px;">CAUTION, limit exposure with surgical mask.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:185px;">Tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA)</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">678937</td>
			<td style="width:185px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:185px;">L-Ascorbic Acid</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">A7506</td>
			<td style="width:185px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:185px;">Phosphate Buffer Saline</td>
			<td style="width:185px;">Invitrogen</td>
			<td style="width:185px;">14190144</td>
			<td style="width:185px;"></td>
		</tr>
		<tr height="168">
			<td height="168" style="height:168px;width:185px;">Donkey Serum</td>
			<td style="width:185px;">Sigma Aldrich</td>
			<td style="width:185px;">D9663</td>
			<td style="width:185px;">Donkey serum contaminated items are considered bio-hazardous material and should be disposed of accordingly. Various other compounds (e.g. BSA) are available and serve this purpose.</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:185px;">12-Well Polystyrene Plate</td>
			<td style="width:185px;">Thermo Scientifit - NUNC</td>
			<td style="width:185px;">07-200-81</td>
			<td style="width:185px;">Plates can be purchased form a number of suppliers with varying dimensions.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:185px;">DBCO-PEG4-Biotin</td>
			<td style="width:185px;">Clickchemistytools</td>
			<td style="width:185px;">A105P4-10</td>
			<td style="width:185px;">Solubilized in DMF</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Streptavidin, Alexa Fluor 488 Conjugate</td>
			<td style="width:185px;">Life Technologies</td>
			<td style="width:185px;">S-11223</td>
			<td style="width:185px;">Solubilized in PBS</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:185px;">Streptavidin, Alexa Fluor 546 conjugate</td>
			<td style="width:185px;">Life Technologies</td>
			<td style="width:185px;">S-11225</td>
			<td style="width:185px;">Solubilized in PBS</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:185px;">Nikon A1-R Confocal Microscope</td>
			<td style="width:185px;">Nikon</td>
			<td style="width:185px;">Nikon Eclipse Ti, A1R</td>
			<td style="width:185px;">An epifluorescent microscope is sufficient to image functionalized micropatterned substrates.</td>
		</tr>
	</tbody>
</table>

fabricating complex culture substrates using robotic microcontact printing (r-&#181;cp) and sequential nucleophilic substitution

In tissue engineering, it is desirable to exhibit spatial control of tissue morphology and cell fate in culture on the micron scale. Culture substrates presenting grafted poly(ethylene glycol) (PEG) brushes can be used to achieve this task by creating microscale, non-fouling and cell adhesion resistant regions as well as regions where cells participate in biospecific interactions with covalently tethered ligands. To engineer complex tissues using such substrates, it will be necessary to sequentially pattern multiple PEG brushes functionalized to confer differential bioactivities and aligned in microscale orientations that mimic in vivo niches. Microcontact printing (&#956;CP) is a versatile technique to pattern such grafted PEG brushes, but manual &#956;CP cannot be performed with microscale precision. Thus, we combined advanced robotics with soft-lithography techniques and emerging surface chemistry reactions to develop a robotic microcontact printing (R-&#956;CP)-assisted method for fabricating culture substrates with complex, microscale, and highly ordered patterns of PEG brushes presenting orthogonal &#8216;click&#8217; chemistries. Here, we describe in detail the workflow to manufacture such substrates.

The use of manual alignment &#956;CP techniques to engineer culture substrates with arrays of PEG-grafted brushes functionalized with orthogonal &#8220;click&#8221; chemistries has been demonstrated in previous work6. However, this offers minimal control of pattern orientation and often results in overlap of functionalized areas. Here, a novel R-&#956;CP system is used to overcome this limitation, and its ability to accurately pattern an array of PEG brush annuli with 300 &#956;m ID and 600 &#956;m OD presenti...

Watch this Scientific Journal Video about Fabricating Complex Culture Substrates Using Robotic Microcontact Printing R-Ã‚ÂµCP and Sequential Nucleophilic Substitution at JoVE.com

Fabricating Complex Culture Substrates Using Robotic Microcontact Printing R-Ãƒâ€šÃ‚ÂµCP and Sequential Nucleophilic Substitution

Cell culture substrates functionalized with microscale patterns of biological ligands have immense utility in the field of tissue engineering. Here, we demonstrate the versatile and automated manufacture of tissue culture substrates with multiple, micropatterned poly(ethylene glycol) brushes presenting orthogonal chemistries that enable spatially precise and site-specific immobilization of biological ligands.

Fabricating Complex Culture Substrates Using Robotic Microcontact Printing (R-&#181;CP) and Sequential Nucleophilic Substitution

In tissue engineering, it is desirable to exhibit spatial control of tissue morphology and cell fate in culture on the micron scale. Culture substrates ...

Research

JoVE Journal

Bioengineering

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A central question in developmental neurobiology is how neural stem and progenitor cells form the brain. To answer this question, one needs to label, ...