Mutemi, K. N. | bioRxiv Science

bioRxiv2024

A genome resource for the marine annelid Platynereis dumerilii

The marine annelid Platynereis dumerilii is a model organism used in many research areas including evolution and development, neurobiology, ecology and regeneration. Here we present the genomes of P. dumerilii (laboratory culture reference and a single individual assembly) and of the closely related P. massiliensis and P. megalops (single individual assembly) to facilitate comparative genomic approaches and help explore Platynereis biology. We used long-read sequencing technology and chromosomal-conformation capture along with extensive transcriptomic resources to obtain and annotate a draft genome assembly of [~]1.47 Gbp for P. dumerilii, of which more than half represent repeat elements. We predict around 29,000 protein-coding genes, with relatively large intron sizes, over 38,000 non-coding genes, and 105 miRNA loci. We further explore the high genetic variation ([~]3% heterozygosity) within the Platynereis species complex. Gene ontology reveals the most variable loci to be associated with pigmentation, development and immunity. The current work sets the stage for further development of Platynereis genomic resources.

genomics↗

bioRxiv2018

Muscleblind regulates Drosophila Dscam2 cell-type-specific alternative splicing

Alternative splicing of genes increases the number of distinct proteins in a cell. In the brain it is highly prevalent, presumably because proteome diversity is crucial for establishing the complex circuitry between trillions of neurons. To provide individual cells with different repertoires of protein isoforms, however, this process must be regulated. Previously, we found that the mutually exclusive alternative splicing of a cell surface protein, Dscam2 produces two isoforms (exon 10A and 10B) with unique binding properties. This splicing event is tightly regulated and crucial for maintaining axon terminal size, dendritic morphology and synaptic numbers. Here, we show that Drosophila Muscleblind (Mbl), a conserved splicing factor implicated in myotonic dystrophy, controls Dscam2 alternative splicing. Removing mbl from cells that normally express isoform B induces the expression of isoform A and eliminates the expression of B, demonstrating that Mbl represses one alternative exon and selects the other. Mbl mutants exhibit phenotypes that are also observed in flies engineered to express a single isoform. Consistent with these observations, mbl expression is cell-type-specific and correlates with the expression of isoform B. Our study demonstrates how the regulated expression of a splicing factor is sufficient to provide neurons with unique protein isoforms crucial for development.

neuroscience↗