Abstract
The RNA export pathway is essential for export-competent mRNAs to pass from the nucleus into the cytoplasm, and thus is essential for protein production and normal function of cells. Drosophila with partial loss of function of Nxt1, a core factor in the pathway, show reduced viability and male and female sterility. The male sterility has previously been shown to be caused by defects in testis-specific gene expression, particularly of genes without introns. Here we describe a specific defect in growth and maintenance of the larval muscles, leading to muscle degeneration in Nxt1 mutants. RNAseq revealed reduced expression of mRNAs of many genes in Nxt1 mutant muscles. Despite this, the degeneration was rescued by increased expression of a single gene, the costamere component tn (abba), in muscles. Genes under-expressed in the mutant typically have long introns, and most normally encode circular RNAs in addition to mRNAs. This is the first report of a specific role for the RNA export pathway gene Nxt1 in muscle integrity. Our data on Nxt1 links the mRNA export pathway to a global role in mRNA expression of genes that also produce circular RNAs, in vivo.
