Roles of the cumulus-oocyte transzonal network and the Fragile X protein family in oocyte competence.

In brief: RNA granules travel through the cumulus cell network of transzonal projections which is associated with oocyte developmental competence, and RNA packaging involves RNA-binding proteins of the Fragile X protein family. Abstract: The determinants of oocyte developmental competence have puzzled scientists for decades. It is known that follicular conditions can nurture the production of a high-quality oocyte, but the underlying mechanisms remain unknown. Somatic cumulus cells most proximal to the oocyte are known to have cellular extensions that reach across the zona pellucida and contact with the oocyte plasma membrane. Herein, it was found that transzonal projections (TZPs) network quality is associated with developmental competence. Knowing that ribonucleoparticles are abundant within TZPs, the distribution of RNA-binding proteins was studied. The Fragile X-related proteins (FXR1P and FXR2P) and two partnering protein families, namely cytoplasmic FMRP-interacting protein and nuclear FMRP-interacting protein, exhibited distinctive patterns consistent with roles in regulating mRNA packaging, transport, and translation. The expression of green fluorescent protein (GFP)-FMRP fusion protein in cumulus cells showed active granule formation and their transport and transfer through filipodia connecting with neighboring cells. Near the projections' ends was found the cytoskeletal anchoring protein Filamin A and active protein synthesis sites. This study highlights key proteins involved in delivering mRNA to the oocyte. Thus, cumulus cells appear to indeed support the development of high-quality oocytes via the transzonal network.

Design and validation of a 63K genome-wide SNP-genotyping platform for caribou/reindeer (Rangifer tarandus).

BACKGROUND: Development of large single nucleotide polymorphism (SNP) arrays can make genomic data promptly available for conservation problematic. Medium and high-density panels can be designed with sufficient coverage to offer a genome-wide perspective and the generated genotypes can be used to assess different genetic metrics related to population structure, relatedness, or inbreeding. SNP genotyping could also permit sexing samples with unknown associated metadata as it is often the case when using non-invasive sampling methods favored for endangered species. Genome sequencing of wild species provides the necessary information to design such SNP arrays. We report here the development of a SNP-array for endangered Rangifer tarandus using a multi-platform sequencing approach from animals found in diverse populations representing the entire circumpolar distribution of the species. RESULTS: From a very large comprehensive catalog of SNPs detected over the entire sample set (N = 894), a total of 63,336 SNPs were selected. SNP selection accounted for SNPs evenly distributed across the entire genome (~ every 50Kb) with known minor alleles across populations world-wide. In addition, a subset of SNPs was selected to represent rare and local alleles found in Eastern Canada which could be used for ecotype and population assignments - information urgently needed for conservation planning. In addition, heterozygosity from SNPs located in the X-chromosome and genotyping call-rate of SNPs located into the SRY gene of the Y-chromosome yielded an accurate and robust sexing assessment. All SNPs were validated using a high-throughput SNP-genotyping chip. CONCLUSION: This design is now integrated into the first genome-wide commercially available genotyping platform for Rangifer tarandus. This platform would pave the way to future genomic investigation of populations for this endangered species, including estimation of genetic diversity parameters, population assignments, as well as animal sexing from genetic SNP data for non-invasive samples.