[BK21 Plus Seminar] ▶Subject: A cell-type specific transcriptional repressor directs selective upregulation of terminal differentiation program ▶Speaker: Jongmin Kim, PhD.(Stanford University School of Medicine) ▶Date: 4:00 PM/Feb. 15(Mon.)/2016 ▶Place: Conference room(#179), Postech Biotech Center *Abctract A critical regulatory point in adult stem cell lineages is the switch from proliferation of transit amplifying (TA) progenitors to onset of terminal differentiation. Key to proper differentiation is ability to turn on lineage specific gene expression programs while maintaining transcriptional silence of genes expressed in other cell types. By synchronous in vivo differentiation of TA cells in the male germ line stem cell lineage of Drosophila, we identified the first new transcripts upregulated as TA cells switch from mitotically dividing spermatogonia to differentiating spermatocytes. Functional analysis of the 43 earliest transcripts identified a novel gene, kumgang (kmg), encoding a 6 C2H2-type zinc finger protein expressed specifically in male germ cells starting in early spermatocytes and localized to chromatin. Loss of Kmg by knock down as well as CRISPR-Cas9 mediated knock out resulted in strong defects in differentiation and kmg-/- spermatids failed to elongate to make functional sperm. Analysis of transcripts in kmg knock down testes showed dramatic upregulation of over 500 genes normally expressed in specific somatic cell types or organs but not in testis. Surprisingly, for spermatocytes in which the repressor was knocked down, testis Meiotic Arrest Complex (tMAC), the transcriptional activator of spermatocyte-specific genes was responsible for the misexpression of somatic genes. Thus through cell-type specific expression of a transcriptional repressor, Kmg, the developmental program prevents collateral damage expression of somatic specific transcripts inappropriate for the lineage as the genome becomes open for expression of the germ line terminal differentiation program. Our findings highlight how the coordinated action of a cell-type specific transcriptional repressor and a promiscuous activator directs selective gene activation. ▶Inquiry: Prof. Sung Ho Ryu (279-2292) * This seminar will be given in English. please refrain from taking photos during seminars. *