A Missense Mutation in PRPF6 Causes Impairment of pre-mRNA Splicing and Autosomal-Dominant Retinitis Pigmentosa

Abstract

Retinitis pigmentosa (RP) is an inherited form of retinal degeneration that leads to progressive visual-field constriction and blindness. Although the disease manifests only in the retina, mutations in ubiquitously expressed genes associated with the tri-snRNP complex of the spliceosome have been identified in patients with dominantly inherited RP. We screened for mutations in PRPF6 (NM_012469.3), a gene on chromosome 20q13.33 encoding an essential protein for tri-snRNP assembly and stability, in 188 unrelated patients with autosomal-dominant RP and identified a missense mutation, c.2185C>T (p.Arg729Trp). This change affected a residue that is conserved from humans to yeast and cosegregated with the disease in the family in which it was identified. Lymphoblasts derived from patients with this mutation showed abnormal localization of endogenous PRPF6 within the nucleus. Specifically, this protein accumulated in the Cajal bodies, indicating a possible impairment in the tri-snRNP assembly or recycling. Expression of GFP-tagged PRPF6 in HeLa cells showed that this phenomenon depended exclusively on the mutated form of the protein. Furthermore, analysis of endogenous transcripts in cells from patients revealed intron retention for pre-mRNA bearing specific splicing signals, according to the same pattern displayed by lymphoblasts with mutations in other PRPF genes. Our results identify PRPF6 as the sixth gene involved in pre-mRNA splicing and dominant RP, corroborating the hypothesis that deficiencies in the spliceosome play an important role in the molecular pathology of this disease.

An integrative analysis of colon cancer identifies an essential function for PRPF6 in tumor growth

“…Although these mutated splicing factors are ubiquitously expressed, defects are seen in specific cell types or tissues consistent with our data that some cells are more sensitive to perturbations in the tri-snRNP complex. Furthermore, consistent with our own spliceome analysis in PRPF6-depleted cancer cells, these patients have been found to harbor discrete splicing alterations in a relatively small number of genes (Tanackovic et al 2011). Taken together, these data strongly suggest that while complete loss of PRPF6 is not compatible with viability, some cells and tissues are more sensitive to a state of reduced activity.…”

“…This suggestion is supported by the tissue-specific defects seen in several genetic syndromes that are characterized by tri-snRNP insufficiency but are compatible with life. adRP, spinal muscular atrophy (SMA), and mandibulofacial dysostosis with microcephaly syndrome (MFDM) are heritable genetic syndromes that stem from heterozygous mutations or deletions in the SMN gene (SMA) or discrete tri-snRNP factors (adRP and MFDM) and consequently lead to haploinsufficiency and impaired tri-snRNP function (Boulisfane et al 2011;Tanackovic et al 2011;Lines et al 2012). Although these mutated splicing factors are ubiquitously expressed, defects are seen in specific cell types or tissues consistent with our data that some cells are more sensitive to perturbations in the tri-snRNP complex.…”

“…A mutation in PRPF6 (PRPF6 R729W ) in its C-terminal tetraco-peptide repeat (TPR) domain has been reported to impair tri-snRNP assembly and function and lead to a heritable form of RP (Tanackovic et al 2011). To assess whether PRPF6-mediated growth in cancer requires its splicing activity, we tested the ability of PRPF6 mutants that either harbor the PRPF6 R729W RP mutation or lack the TPR domain to restore growth after PRPF6 depletion.…”

“…Components of the spliceosome machinery have been shown to be dysregulated in human disease. One example is the tri-snRNP (small ribonucleoprotein) complex, which consists of U4/U5/U6 proteins and is known to cause an autosomal dominant form of retinitis pigmentosa (adRP) when mutated (Sharp 1988;Tanackovic et al 2011;Will and Lü hrmann 2011). More recently, recurrent somatic mutations have been identified in a number of spliceosome components in cancers (Ebert and Bernard 2011;Wang et al 2011;Yoshida et al 2011;Graubert et al 2012;Hahn and Scott 2012;Imielinski et al 2012;Quesada et al 2012), raising speculation that the spliceosome may play a role in tumor growth.…”

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

“…Ces protéines sont impliquées dans l'assemblage ou le désassemblage du complexe tri-snRNP U4/U6.U5. La mutation c.2185C>T (correspondant à p.Arg729Trp sur la protéine) du gène PRPF6 est associée à un défaut d'assemblage du complexe du fait de la localisation nucléaire aberrante de la protéine dans les corps de Cajal, des sites où prennent place des modifications et l'assemblage de plusieurs snRNP [13]. [26].…”