A defect in the RNA-processing protein HNRPDL causes limb-girdle muscular dystrophy 1G (LGMD1G)

Limb-girdle muscular dystrophies (LGMD) are a heterogeneous group of genetically determined muscle disorders with a primary orpredominant involvement of the pelvic or shoulder girdlemusculature.Morethan 20genes with autosomal recessive (LGMD2A to LGMD2Q) and autosomal dominant inheritance (LGMD1A to LGMD1H) have beenmapped/identified to date. Mutations are known for six among the eightmapped autosomal dominant forms: LGMD1A (myotilin), LGMD1B (lamin A/C), LGMD1C (caveolin-3), LGMD1D (desmin), LGMD1E (DNAJB6), and more recently for LGMD1F (transportin-3). Our group previously mapped the LGMD1G gene at 4q21 in a Caucasian-Brazilian family. We now mapped a Uruguayan family with patients displaying a similar LGMD1G phenotype at the same locus. Whole genome sequencing identified, in both families, mutations in the HNRPDL gene. HNRPDL is a heterogeneous ribonucleoprotein family member, which participates inmRNAbiogenesis and metabolism. Functional studies performed in S. cerevisiae showed that the loss of HRP1 (yeast orthologue) had pronounced effects on both protein levels and cell localizations, and yeast proteome revealed dramatic reorganization of proteins involved in RNA-processing pathways. In vivo analysis showed that hnrpdl is important for muscle development in zebrafish, causing amyopathic phenotype when knocked down. The present study presents a novel association between a muscular disorder and a RNA-related gene and reinforces the importance of RNA binding/processing proteins in muscle development and muscle disease. Understanding the role of these proteins in muscle might open new therapeutic approaches for muscular dystrophies.