Defective minor spliceosome mRNA processing results in isolated familial growth hormone deficiency

Abstract

The molecular basis of a significant number of cases of isolated growth hormone deficiency remains unknown. We describe three sisters affected with severe isolated growth hormone deficiency and pituitary hypoplasia caused by biallelic mutations in the RNPC3 gene, which codes for a minor spliceosome protein required for U11/U12 small nuclear ribonucleoprotein (snRNP) formation and splicing of U12-type introns. We found anomalies in U11/U12 di-snRNP formation and in splicing of multiple U12-type introns in patient cells. Defective transcripts include preprohormone convertases SPCS2 and SPCS3 and actin-related ARPC5L genes, which are candidates for the somatotroph-restricted dysfunction. The reported novel mechanism for familial growth hormone deficiency demonstrates that general mRNA processing defects of the minor spliceosome can lead to very narrow tissue-specific consequences.Subject Categories Genetics, Gene Therapy ' Genetic Disease; Metabolism

MECHANISMS IN ENDOCRINOLOGY: Novel genetic causes of short stature

“…Isolated GHD can also be caused by biallelic mutations in RNPC3, which encodes a minor spliceosome protein required for U11/U12 small nuclear ribonucleoprotein (snRNP) formation and splicing of U12-type introns (33). Compound heterozygosity for a gene encoding a protein important for ciliary function (IFT172) can cause functional GHD, pituitary hypoplasia, and ectopic posterior pituitary (34), and also Alström syndrome, caused by a mutation of ALMS1 encoding a protein localized to the centrosomes and basal bodies of ciliated cells (35) is associated with GHD.…”

L’épissage des ARN pré-messagers : quand le splicéosome perd pied

“…Plusieurs autres pathologies affectant l'épissage en trans ont égale-ment été rapportées, dont une délétion du gène SF3B4 (splicing factor 3b subunit 4) associée au syndrome de Nager, une affection caractéri-sée par des dysostoses acrofaciales 2 [14], ou encore la Clericuzio-type poikiloderma, une maladie associée à un défaut de maturation du snARN U6 [15]. En outre, plusieurs mutations affectant le fonctionnement du splicéosome mineur ont été caractérisées dont celles à l'origine d'une déficience en hormone de croissance [16] ou d'une forme de nanisme affectant le gène MOPD I (microcephalic osteodysplastic primordial dwarfism) [17], ou encore de la sclérose latérale amyotrophique (SLA) [18]. Au-delà des mutations germinales, un large ensemble de mutations acquises ont été identifiées, en particulier dans les cancers.…”

Regulation of gene expression through inefficient splicing of U12-type introns

“…In contrast, mutations in the 65K gene lead to rather dramatic activation of cryptic U2-type splice sites, but a very mild disease (IGHD1) phenotype with pituitary hypoplasia resulting in postnatal dwarfism, but apparently no other major symptoms. 28 While detailed transcriptome analysis of the MOPD1/TALS patients has not yet been described, the results seem somewhat counterintuitive, with more severe splicing defects leading to a milder disease. One possible explanation is that that perhaps the activation of cryptic U2-type splice sites seen with IGHD1 are better tolerated than the intron retention events reported with MOPD1/TALS.…”

“…Importantly, this has been observed not only in human or mammalian cells, but also in Arabidopsis. 29 In contrast, under normal conditions the unspliced U12-type introns accumulate but there is no indication of concomitant activation of nearby cryptic splice sites, 19,20,28 arguing that U12-type introns are in fact recognized with similar efficiency as U2-type introns, but one or more subsequent steps in the spliceosome assembly or catalytic activation of the spliceosome are either slow or fail altogether, thus resulting in the elevated intron retention signal seen with the RT-PCR and RNAseq analyses (Fig. 1).…”

“…27 Regardless of whether the U12-type introns are spliced slowly or inefficiently, the molecular events responsible for the elevated retention levels of U12-type introns appear to take place after the intron recognition step. Inhibition of intron recognition step either by human disease-causing mutations 28 or by knocking down specific protein components in the U11/U12 di-snRNP responsible for the initial intron recognition 29,30 all lead to, in addition to a defect in the splicing of U12-type introns, activation of cryptic U2-type splice sites in the vicinity of a subset of U12-type introns. Importantly, this has been observed not only in human or mammalian cells, but also in Arabidopsis.…”