Spatiotemporal Gene Expression Analysis of theCaenorhabditis elegansGermline Uncovers a Syncytial Expression Switch

Abstract

Developmental programs are executed by tightly controlled gene regulatory pathways. Here, we combined the unique sample retrieval capacity afforded by laser capture microscopy with analysis of mRNA abundance by CEL-Seq (cell expression by linear amplification and sequencing) to generate a spatiotemporal gene expression map of the Caenorhabditis elegans syncytial germline from adult hermaphrodites and males. We found that over 6000 genes exhibit spatiotemporally dynamic expression patterns throughout the hermaphrodite germline, with two dominant groups of genes exhibiting reciprocal shifts in expression at late pachytene during meiotic prophase I. We found a strong correlation between restricted spatiotemporal expression and known developmental and cellular processes, indicating that these gene expression changes may be an important driver of germ cell progression. Analysis of the male gonad revealed a shift in gene expression at early pachytene and upregulation of subsets of genes following the meiotic divisions, specifically in early and late spermatids, mostly transcribed from the X chromosome. We observed that while the X chromosome is silenced throughout the first half of the gonad, some genes escape this control and are highly expressed throughout the germline. Although we found a strong correlation between the expression of genes corresponding to CSR-1-interacting 22G-RNAs during germ cell progression, we also found that a large fraction of genes may bypass the need for CSR-1-mediated germline licensing. Taken together, these findings suggest the existence of mechanisms that enable a shift in gene expression during prophase I to promote germ cell progression.

Multivalent weak interactions between assembly units drive synaptonemal complex formation

“…(A) List of SYP-2::GFP binding proteins identified by IP and MS. K09H9.1 is a predicted paralog of SYP-5 and SYP-6, but it was not detected in the immunoprecipitates. (B) SYP proteins show comparable translation rates, and the translation of K09H9.1 was not detected (data extracted from Tzur et al [2018] ). Scatter plots with bar graphs depict mean ± SEM of data from two biological replicates.…”

Progression of Meiosis Is Coordinated by the Level and Location of MAPK Activation Via OGR-2 in Caenorhabditis elegans

“…Currently, little is known about this domain beyond its presence in this group of proteins. The domain is present in the N-terminus of the 349-aa protein encoded by F52H3.4, a previously uncharacterized gene expressed in the germline (Reinke et al 2000;Ortiz et al 2014;Diag et al 2018;Tzur et al 2018) ( Figure S1A). Below, we describe multiple roles for F52H3.4 in the hermaphrodite adult germline.…”

Chromosome Integrity is Required for the Initiation of Meiotic Sex Chromosome Inactivation inCaenorhabditis elegans

“…In the gonads of hermaphroditic C. elegans, the two X chromosomes are silenced from the proliferative nuclei until late pachytene, and then transcription resumes [26][27][28][29]54 . During early meiotic stages, the chromatin of X chromosomes is enriched with modifications correlated with low transcriptional activity such as histone H3 trimethylated at lysine 27 (H3K27me3) 55 .…”