Journal: Nature
Article Title: Developmental dynamics of two bipotent thymic epithelial progenitor types
doi: 10.1038/s41586-022-04752-8
Figure Lengend Snippet: a , Schematic of the CRISPR–Cas9-based barcoding system. DSB, double-strand break. b , Location of the target site in exon 3 of the mouse Hprt gene. c , Examples of barcodes; the germline sequence is shown with the sgRNA target and protospacer adjacent motif (PAM) sequences indicated at top. Nucleotide additions and deletions (dashes) are indicated in red. d , Frequencies of individual barcodes in decreasing order. e , Number of Foxn1 -expressing TECs in the thymic rudiment of E12.5 embryos (left; n = 5) and numbers of different barcodes in the thymi of mice of different ages (right): E16.5, n = 6; P0, n = 5; P12–P15, n = 11; >P16, n = 12. The dotted lines indicate the range of the numbers of progenitors previously inferred from medullary islet counts in adult mice . f , Enrichment of shared barcodes in the Ly51 – UEA-1 + mTEC and Ly51 + UEA-1 – cTEC fractions of mice of different ages. Enrichment values were significantly different in the comparison of mice at P0 and >3 weeks (w) ( P = 0.009, one-sided Wilcoxon test). E16.5, n = 6; P0, n = 5; ~2 weeks, n = 11; >3 weeks, n = 11. For e and f , boxes extend from the 25th to 75th percentile; whiskers extend to the largest and smallest values; and the median is indicated. See the for a definition of the enrichment value E m . g , Co-occurrence probability of rare barcodes across pairs of samples highlighting enhanced co-occurrence in mTEC (m) and cTEC (c) fractions of the same mouse; individual mice are identified by number. Data are shown for n = 18 mice. h – k , P values (–log 10 ) of barcode frequencies indicating co-occurrence of individual barcodes in progenitor and mature TEC fractions (as defined in Fig. ) at different time points. For g – k , P values were calculated as described in the and corrected for multiple testing by the Benjamini–Hochberg method. The red numbers refer to clones discussed in the text.
Article Snippet: The hU6-sgRNA Hprt transgene was cloned as a NotI fragment into the Bluescript vector and consists of the human U6 promotor (nucleotides 1–264 in GenBank accession number JN255693 ) followed by the mouse Hprt target sequence (5′-GATGGGAGGCCATCACATTGG-3′; nucleotides 255–274 in GenBank accession number J00423 ), the sgRNA backbone (nucleotides 218–139 (reverse complement) in Addgene plasmid 42250) and a short 3′ sequence (TTTTTTGGAA); for injection into fertilized eggs, the construct was linearized with SacI.
Techniques: CRISPR, Sequencing, Expressing, Clone Assay