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May 27

Identifying regulators of sex - specific gonadal development

Dr. Mary Kroetz, Post-Doctoral Fellow, Department of Genetics/Cell Biology, University of Minnesota-Twin Cities campus

Monday, May 27th, 2013
3:30 – 4:30 pm / Olin 141
Mary Kroetz, UMN

The C. elegans gonad originates in the embryo with the coalescence of a four-cell primordium composed of two somatic precursor cells (Z1/Z4) that flank two germ line precursor cells (Z2/Z3). The gonadal primordium is morphologically identical in the two sexes until the division of Z1/Z4. With the division of these cells, the gonadal primordium begins to develop via one of two distinct sex-specific programs of organogenesis. Despite the extensive sexual dimorphism and previously defined cell lineages of the gonad, the genetic pathways that direct the development of this organ, including its sex-specific development, remain largely unknown. To define the genetic networks that regulate gonadal development in both sexes, we employed cell-specific transcriptional profiling of Z1/Z4 using RNA-seq to identify the early gonadal regulators. Single sex populations of animals were generated by employing sex determination pathway mutants. A Z1/Z4-specific gfp reporter was used to isolate these cells by FACS from dissociated mid-L1 larval cells, just prior to the division of Z1/Z4 when the first sex-specific differences of the gonad arise.  A few hundred Z1/Z4-enriched transcripts were identified for both hermaphrodites and fully masculinized XX-pseudomales, and a much smaller number of sex-specific Z1/Z4-enriched transcripts were also identified. The majority of transcripts with known Z1/Z4-enriched expression were identified by this method, including fkh-6, gem-4, and pes-1, and a number of novel Z1/Z4-enrichedtranscripts, including previously unannotated isoforms, have subsequently been validated by reporter analysis, confirming the effectiveness of this approach. Loss of function phenotypes are being determined by RNAi depletion and mutant analysis, with emphasis on transcripts that are sex-specifically Z1/Z4-enriched. Taking advantage of the recent innovations in larval dissociation and cell-specific RNA-seq, this work, which focuses on identifying the genetic networks responsible for the sex-specific developmental of the C. elegans gonad from a biopotential promordium, should advance our understanding of the regulatory logic and mechanisms underlying sexually dimorphicorganogenesis and cell fate determination.

Sponsored by Biology. Contact: Lorie Tuma, x4884