Multiple division cycles without growth are a characteristic feature of early embryogenesis. The female germline deposits proteins and RNAs into oocytes to support these divisions, which lack many of the quality control mechanisms operating in somatic cells undergoing growth. How the composition of the oocyte maternal load is regulated to ensure its ability to support early embryogenesis is not known. Here we describe a small RNA-Argonaute pathway, operating in the C. elegans germline, that ensures early embryonic divisions by employing catalytic slicing activity to broadly tune, instead of silence, germline gene expression. Misregulation of one target, a kinesin-13 microtubule depolymerase, underlies a major embryonic phenotype associated with pathway loss. Tuning of target expression is guided by small RNA density, which must ultimately be related to target sequence. Thus, C. elegans employs a single catalytic Argonaute for small RNA-mediated tuning of the mRNA levels of germline-expressed genes that support early embryogenesis. Overall design: mRNA profiling of 2 replicates each for 3 genotypes of adult-stage C. elegans worms
A Small RNA-Catalytic Argonaute Pathway Tunes Germline Transcript Levels to Ensure Embryonic Divisions.
Specimen part, Cell line, Subject
View SamplesA specific subpopulation of neural progenitor cells, the basal radial glia cells (bRGCs) of the outer subventricular zone (OSVZ), are thought to have a key role in the evolutionary expansion of mammalian neocortex. In the developing lissencephalic mouse neocortex, bRGCs exist at low abundance and show significant molecular differences from bRGCs in developing gyrencephalic species. Here, we demonstrate that developing mouse medial neocortex, in contrast to the canonically studied lateral neocortex, exhibits an OSVZ and an abundance of bRGCs similar to that in developing gyrencephalic neocortex. Unlike bRGCs in developing mouse lateral neocortex, the bRGCs in medial neocortex exhibit human bRGC-like gene expression, including expression of Hopx, a human bRGC marker. Disruption of Hopx expression in mouse embryonic medial neocortex and forced Hopx expression in mouse embryonic lateral neocortex demonstrate that Hopx is required and sufficient, respectively, for a bRGC abundance as found in developing gyrencephalic neocortex. Taken together, our data identify a novel bRGC subpopulation in developing mouse medial neocortex that is highly related to bRGCs of developing gyrencephalic neocortex. Overall design: 221 single-cell transcriptomes from microdissected medial neocortex of E18.5 mouse embryos (two independent analyses using a pool of 8 neocortices each).
A novel population of Hopx-dependent basal radial glial cells in the developing mouse neocortex.
Sex, Specimen part, Cell line, Subject
View SamplesNeuronal migration disorders such as lissencephaly and subcortical band heterotopia (SBH) are associated with epilepsy and intellectual disability. Doublecortin (DCX), LIS1 and alpha1-tubulin (TUBA1A), are mutated in these disorders, however corresponding mouse mutants do not show heterotopic neurons in the neocortex. On the other hand, the spontaneously arisen HeCo mouse mutant displays this phenotype. The study of this model reveals novel mechanisms of heterotopia formation. While, HeCo neurons migrate at the same speed as WT, abnormally distributed dividing progenitors were found throughout the cortical wall from E13. Through genetic studies we identified Eml1 as the mutant gene in HeCo mice. No full length transcripts of Eml1 were identified due to a retrotransposon insertion in an intron. Re-expression of Eml1, coding for a microtubule-associated protein, rescues the HeCo progenitor phenotype. We further show that EML1 is mutated in giant ribbon-like heterotopia in human. Our data link abnormal spindle orientations, ectopic progenitors and severe heterotopia in mouse and human.
Mutations in Eml1 lead to ectopic progenitors and neuronal heterotopia in mouse and human.
Specimen part
View SamplesIntegrator (INT) is an RNA polymerase II (RNAPII)-associated complex that was recently identified to have a broad role in both RNA processing and transcription regulation. INT has at least 14 subunits, but INT germline mutations causing human disease have not been reported. We identified mutations in the Integrator Complex Subunit 8 gene (INTS8) causing a rare neurodevelopmental syndrome. In patient cells we identified significant disturbance of gene expression and RNA processing. Also, we show that injection of ints8 oligonucleotide morpholinos into zebrafish embryos leads to prominent underdevelopment of the head demonstrating the evolutionary conserved requirement of INTS8 in brain development. Overall design: RNA sequencing was carried out using RNA samples from fibroblasts from two individuals with germline bi-allelic INTS8 mutations and from two healthy individuals
Human mutations in integrator complex subunits link transcriptome integrity to brain development.
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