The CGG repeat expansion in RILPL1 is associated with oculopharyngodistal myopathy type 4.

Recent studies indicate that CGG repeat expansions in LRP12, GIPC1, and NOTCH2NLC are associated with oculopharyngodistal myopathy (OPDM) types 1, 2, and 3, respectively. However, some clinicopathologically confirmed OPDM cases continue to have unknown genetic causes. Here, through a combination of long-read whole-genome sequencing (LRS), repeat-primed polymerase chain reaction (RP-PCR), and fluorescence amplicon length analysis PCR (AL-PCR), we found that a CGG repeat expansion in the 5' UTR of RILPL1 is associated with familial and simplex OPDM type 4 (OPDM4). The number of repeats ranged from 139 to 197. Methylation analysis indicates that the methylation levels in RILPL1 were unaltered in OPDM4 individuals. Analyses of muscle biopsies suggested that the expanded CGG repeat might be translated into a toxic poly-glycine protein that co-localizes with p62 in intranuclear inclusions. Moreover, analyses suggest that the toxic RNA gain-of-function effects also contributed to the pathogenesis of this disease. Intriguingly, all four types of OPDM have been found to be associated with the CGG repeat expansions located in 5' UTRs. This finding suggests that a common pathogenic mechanism, driven by the CGG repeat expansion, might underlie all cases of OPDM.

Clinical and pathological characteristics of OPDM4 patients in advanced disease.

INTRODUCTION/AIMS: Oculopharyngodistal myopathy type 4 (OPDM4) arises from a CGG repeat expansion in the 5' UTR of the RILPL1 gene. Reported cases of OPDM4 have been limited. The aim of this study was to investigate the clinical and myopathological characteristics of OPDM4 patients with advanced disease. METHODS: We assessed a total of 8 affected and 12 unaffected individuals in an OPDM4 family with autosomal dominant inheritance. Muscle biopsy tissue from the proband underwent histological, enzyme histochemical, and immunohistochemical stains, and electron microscopy analysis. Whole exome sequencing and repeat primer PCR (RP-PCR) were conducted to investigate underlying variants. RESULTS: OPDM4 patients displayed a progressive disease course. Most experienced lower limb weakness and diminished walking ability in their 20s and 30s, followed by ptosis, ophthalmoplegia, swallowing difficulties, and dysarthria in their 30s to 50s, By their 50s to 70s, they became non-ambulatory. Muscle magnetic resonance imaging (MRI) of the proband in advanced disease revealed severe fatty infiltration of pelvic girdle and lower limb muscles. Biopsied muscle tissue exhibited advanced changes typified by adipose connective tissue replacement and the presence of multiple eosinophilic and p62-positive intranuclear inclusions. Immunopositivity for the intranuclear inclusions was observed with anti-glycine antibody and laboratory-made polyA-R1 antibody. RP-PCR unveiled an abnormal CGG repeat expansion in the 5' UTR of the RILPL1 gene. DISCUSSION: The clinical and radiological features in this family broaden the phenotypic spectrum of OPDM4. The presence of intranuclear inclusions in the proliferative adipose connective tissues of muscle biopsy specimens holds diagnostic significance for OPDM4 in advanced disease.

A large pedigree study confirmed the CGG repeat expansion of RILPL1 Is associated with oculopharyngodistal myopathy.

BACKGROUND: Oculopharyngodistal myopathy (OPDM) is an autosomal dominant adult-onset degenerative muscle disorder characterized by ptosis, ophthalmoplegia and weakness of the facial, pharyngeal and limb muscles. Trinucleotide repeat expansions in non-coding regions of LRP12, G1PC1, NOTCH2NLC and RILPL1 were reported to be the etiologies for OPDM. RESULTS: In this study, we performed long-read whole-genome sequencing in a large five-generation family of 156 individuals, including 21 patients diagnosed with typical OPDM. We identified CGG repeat expansions in 5'UTR of RILPL1 gene in all patients we tested while no CGG expansion in unaffected family members. Repeat-primed PCR and fluorescence amplicon length analysis PCR were further confirmed the segregation of CGG expansions in other family members and 1000 normal Chinese controls. Methylation analysis indicated that methylation levels of the RILPL1 gene were unaltered in OPDM patients, which was consistent with previous studies. Our findings provide evidence that RILPL1 is associated OPDM in this large pedigree. CONCLUSIONS: Our results identified RILPL1 is the associated the disease in this large pedigree.

The LRRK2 signaling network converges on a centriolar phospho-Rab10/RILPL1 complex to cause deficits in centrosome cohesion and cell polarization.

The Parkinson's-disease-associated LRRK2 kinase phosphorylates multiple Rab GTPases including Rab8 and Rab10, which enhances their binding to RILPL1 and RILPL2. The nascent interaction between phospho-Rab10 and RILPL1 blocks ciliogenesis in vitro and in the intact brain, and interferes with the cohesion of duplicated centrosomes in dividing cells. We show here that regulators of the LRRK2 signaling pathway including vps35 and PPM1H converge upon causing centrosomal deficits. The cohesion alterations do not require the presence of other LRRK2 kinase substrates including Rab12, Rab35 and Rab43 or the presence of RILPL2. Rather, they depend on the RILPL1-mediated centrosomal accumulation of phosphorylated Rab10. RILPL1 localizes to the subdistal appendage of the mother centriole, followed by recruitment of the LRRK2-phosphorylated Rab proteins to cause the centrosomal defects. The centrosomal alterations impair cell polarization as monitored by scratch wound assays which is reverted by LRRK2 kinase inhibition. These data reveal a common molecular pathway by which enhanced LRRK2 kinase activity impacts upon centrosome-related events to alter the normal biology of a cell.

Advances in elucidating the function of leucine-rich repeat protein kinase-2 in normal cells and Parkinson's disease.

Autosomal dominant missense mutations that hyperactivate the leucine-rich repeat protein kinase-2 (LRRK2) are a common cause of inherited Parkinson's disease and therapeutic efficacy of LRRK2 inhibitors is being tested in clinical trials. In this review, we discuss the nuts and bolts of our current understanding of how the LRRK2 is misregulated by mutations and how pathway activity is affected by LRRK2 binding to membrane, microtubule filaments, and 14-3-3, as well as by upstream components such as Rab29 and VPS35. We discuss recent work that points toward a subset of Rab proteins comprising key physiological substrates that bind new sets of effectors, such as RILPL1/2, JIP3 and JIP4 after phosphorylation by LRRK2. We explore what is known about how LRRK2 regulates ciliogenesis, the endosomal-lysosomal system, immune responses and interplay with alpha-synuclein and tau and how this might be linked to Parkinson's' disease.