Inactivity of Peptidase ClpP Causes Primary Accumulation of Mitochondrial Disaggregase ClpX with Its Interacting Nucleoid Proteins, and of mtDNA

From MDPI via Jisc Publications RouterHistory: accepted 2021-11-25, pub-electronic 2021-11-29Publication status: PublishedFunder: German Network for Mitochondrial Disorders; Grant(s): mitoNET, 01GM1906D, R01HL148153Funder: Action Medical Research; Grant(s): GN2494Funder: Office of the Assistant Secretary for Health; Grant(s): W81XWH-17-1-0052, W81XWH-20-1-0150Biallelic pathogenic variants in CLPP, encoding mitochondrial matrix peptidase ClpP, cause a rare autosomal recessive condition, Perrault syndrome type 3 (PRLTS3). It is characterized by primary ovarian insufficiency and early sensorineural hearing loss, often associated with progressive neurological deficits. Mouse models showed that accumulations of (i) its main protein interactor, the substrate-selecting AAA+ ATPase ClpX, (ii) mitoribosomes, and (iii) mtDNA nucleoids are the main cellular consequences of ClpP absence. However, the sequence of these events and their validity in human remain unclear. Here, we studied global proteome profiles to define ClpP substrates among mitochondrial ClpX interactors, which accumulated consistently in ClpP-null mouse embryonal fibroblasts and brains. Validation work included novel ClpP-mutant patient fibroblast proteomics. ClpX co-accumulated in mitochondria with the nucleoid component POLDIP2, the mitochondrial poly(A) mRNA granule element LRPPRC, and tRNA processing factor GFM1 (in mouse, also GRSF1). Only in mouse did accumulated ClpX, GFM1, and GRSF1 appear in nuclear fractions. Mitoribosomal accumulation was minor. Consistent accumulations in murine and human fibroblasts also affected multimerizing factors not known as ClpX interactors, namely, OAT, ASS1, ACADVL, STOM, PRDX3, PC, MUT, ALDH2, PMPCB, UQCRC2, and ACADSB, but the impact on downstream metabolites was marginal. Our data demonstrate the primary impact of ClpXP on the assembly of proteins with nucleic acids and show nucleoid enlargement in human as a key consequence

Leber Congenital Amaurosis: Comprehensive Survey of the Genetic Heterogeneity, Refinement of the Clinical Definition, and Genotype-Phenotype Correlations as a Strategy for Molecular Diagnosis

Communicated by Jean-Claude Kaplan Leber congenital amaurosis (LCA) is the earliest and most severe form of all inherited retinal dystrophies, responsible for congenital blindness. Disease-associated mutations have been hitherto reported in seven genes. These genes are all expressed preferentially in the photoreceptor cells or the retinal pigment epithelium but they are involved in strikingly different physiologic pathways resulting in an unforeseeable physiopathologic variety. This wide genetic and physiologic heterogeneity that could largely increase in the coming years, hinders the molecular diagnosis in LCA patients. The genotyping is, however, required to establish genetically defined subgroups of patients ready for therapy. Here, we report a comprehensive mutational analysis of the all known genes in 179 unrelated LCA patients, including 52 familial and 127 sporadic (27/127 consanguineous) cases. Mutations were identified in 47.5% patients. GUCY2D appeared to account for most LCA cases of our series (21.2%), followed by CRB1 (10%), RPE65 (6.1%), RPGRIP1 (4.5%), AIPL1 (3.4%), TULP1 (1.7%), and CRX (0.6%). The clinical history of all patients with mutations was carefully revisited to search for phenotype variations. Sound genotype-phenotype correlations were found that allowed us to divide patients into two main groups. The first one includes patients whose symptoms fit the traditional definition of LCA, i.e., congenital or very early cone-rod dystrophy, while the second group gathers patients affected with severe yet progressive rodcone dystrophy. Besides, objective ophthalmologic data allowed us to subdivide each group into two subtypes. Based on these findings, we have drawn decisional flowcharts directing the molecular analysis of LCA genes in a given case. These flowcharts will hopefully lighten the heavy task of genotyping new patients but only if one has access to the most precise clinical history since birth

Genomic analyses in Cornelia de Lange Syndrome and related diagnoses: Novel candidate genes, <scp>genotype–phenotype</scp> correlations and common mechanisms

Cornelia de Lange Syndrome (CdLS) is a rare, dominantly inherited multisystem developmental disorder characterized by highly variable manifestations of growth and developmental delays, upper limb involvement, hypertrichosis, cardiac, gastrointestinal, craniofacial, and other systemic features. Pathogenic variants in genes encoding cohesin complex structural subunits and regulatory proteins (NIPBL, SMC1A, SMC3, HDAC8, and RAD21) are the major pathogenic contributors to CdLS. Heterozygous or hemizygous variants in the genes encoding these five proteins have been found to be contributory to CdLS, with variants in NIPBL accounting for the majority (&gt;60%) of cases, and the only gene identified to date that results in the severe or classic form of CdLS when mutated. Pathogenic variants in cohesin genes other than NIPBL tend to result in a less severe phenotype. Causative variants in additional genes, such as ANKRD11, EP300, AFF4, TAF1, and BRD4, can cause a CdLS‐like phenotype. The common role that these genes, and others, play as critical regulators of developmental transcriptional control has led to the conditions they cause being referred to as disorders of transcriptional regulation (or “DTRs”). Here, we report the results of a comprehensive molecular analysis in a cohort of 716 probands with typical and atypical CdLS in order to delineate the genetic contribution of causative variants in cohesin complex genes as well as novel candidate genes, genotype–phenotype correlations, and the utility of genome sequencing in understanding the mutational landscape in this population

Hydrops fetalis: an unusual prenatal presentation of hereditary congenital lymphedema.

OBJECTIVES: To report a rare case of primary congenital lymphedema (PCL) presenting as hydrops fetalis. METHODS: The patient presented at 33(+4) weeks' gestation with polyhydramnios, massive bilateral hydrothorax, skin edema, scalp edema and minimal ascites. In utero thoracocentesis was performed and delivery was induced. Follow-up at 12 months of age revealed moderate bilateral foot edema with otherwise normal development. RESULTS: The diagnosis of PCL was suspected on the basis of the family history. DNA analysis revealed a novel missense mutation, E1106K, in the tyrosine kinase domain of the vascular endothelial growth factor receptor 3 gene (VEGFR3/FLT4). CONCLUSION: PCL should be considered in the differential diagnosis of hydrops fetalis. Knowledge of the favorable course, variable clinical presentation, therapy options and genetic basis should contribute to better pregnancy counseling and management

Wide clinical spectrum in a family with hereditary lymphedema type I due to a novel missense mutation in VEGFR3.

Hereditary lymphedema type I (HL-I), also known as Milroy disease, is an autosomal dominant disorder characterized by typical phenotype of infantile onset lower-limb lymphedema accompanied by variable expression of recurrent episodes of cellulites, toenail changes, and papillomatosis. Mutations in the vascular endothelial growth factor receptor 3 (VEGFR3), also known as FLT4 gene, which encodes a lymphatic endothelial-specific tyrosine kinase receptor, have been identified as a genetic cause of HL-I. We report a large Muslim Arab family residing in northern Israel with 14 individuals presenting clinical features of HL-I. Genetic analysis revealed novel missense mutation E1106K in the tyrosine kinase domain II of VEGFR3 that cosegregates with the disorder in the family. Most affected individuals presented with bilateral congenital lower-limb lymphedema. Wide intrafamilial phenotypic variability included two asymptomatic individuals, a case of prenatal hydrothorax evolving to hydrops fetalis, and a late-onset complication, yet unreported, of chronic degenerative joint disease of the knees. This report broadens the known "classic" phenotype of HL-I