Perilipin 1: a systematic review on its functions on lipid metabolism and atherosclerosis in mice and humans.

The function of perilipin 1 in human metabolism was recently highlighted by the description of PLIN1 variants associated with various pathologies. These include severe familial partial lipodystrophy and early onset acute coronary syndrome. Additionally, certain variants have been reported to have a protective effect on cardiovascular diseases. The role of this protein remains controversial in mice and variant interpretation in humans is still conflicting. This literature review has two primary objectives (i) to clarify the function of the PLIN1 gene in lipid metabolism and atherosclerosis by examining functional studies performed in cells (adipocytes) and mice and (ii) to understand the impact of PLIN1 variants identified in humans based on the variant's location within the protein and the type of variant (missense or frameshift). To achieve these objectives, we conducted an extensive analysis of the relevant literature on perilipin 1, its function in cellular models and mice, and the consequences of its mutations in humans. We also utilized bioinformatics tools and consulted the Human Genetics Cardiovascular Disease Knowledge Portal to enhance the pathogenicity assessment of PLIN1 missense variants.

Clinical and genetic features of patients suffering from CMT4J.

Mutations in the FIG4 gene have been identified in various diseases, including amyotrophic lateral sclerosis, Parkinson's disease, and Charcot-Marie-Tooth 4 J (CMT4J), with a wide range of phenotypic manifestations. We present eight cases of CMT4J patients carrying the p.Ile41Thr mutation of FIG4. The patients were categorized according to their phenotype. Six patients had a pure CMT; whereas, two patients had a CMT associated with parkinsonism. Three patients had an early onset and exhibited more severe forms of the disease. Three others experienced symptoms in their teenage years and had milder forms. Two patients had a late onset in adulthood. Four patients showed electrophysiological evidence of conduction blocks, typically associated with acquired neuropathies. Consequently, two of them received intravenous immunoglobulin treatment without a significant objective response. Interestingly, two heterozygous patients with the same mutations exhibited contrasting phenotypes, one having a severe early-onset form and the other experiencing a slow disease progression starting at the age of 49. Notably, although 7 out of 8 patients in this study were compound heterozygous for the p.Ile41Thr mutation, only one individual was found to be homozygous for this genetic variant and exhibited an early-onset, severe form of the disease. Additionally, one patient who developed the disease in his youth was also diagnosed with hereditary neuropathy with pressure palsies. Our findings provide insights into the CMT4J subtype by reporting on eight heterogeneous patient cases and highlight the potential for misdiagnosis when conduction blocks or asymmetrical nerve conduction study results are observed in patients with FIG4 mutations.

Genetic landscape of congenital insensitivity to pain and hereditary sensory and autonomic neuropathies.

Congenital insensitivity to pain (CIP) and hereditary sensory and autonomic neuropathies (HSAN) are clinically and genetically heterogeneous disorders exclusively or predominantly affecting the sensory and autonomic neurons. Due to the rarity of the diseases and findings based mainly on single case reports or small case series, knowledge about these disorders is limited. Here, we describe the molecular workup of a large international cohort of CIP/HSAN patients including patients from normally under-represented countries. We identify 80 previously unreported pathogenic or likely pathogenic variants in a total of 73 families in the >20 known CIP/HSAN-associated genes. The data expand the spectrum of disease-relevant alterations in CIP/HSAN, including novel variants in previously rarely recognized entities such as ATL3-, FLVCR1- and NGF-associated neuropathies and previously under-recognized mutation types such as larger deletions. In silico predictions, heterologous expression studies, segregation analyses and metabolic tests helped to overcome limitations of current variant classification schemes that often fail to categorize a variant as disease-related or benign. The study sheds light on the genetic causes and disease-relevant changes within individual genes in CIP/HSAN. This is becoming increasingly important with emerging clinical trials investigating subtype or gene-specific treatment strategies.

Transfusion requirements and complication rate in ß-thalassemia intermedia due to heterozygous ß-globin gene mutation and triplicated α-globin genes.

INTRODUCTION: The heterozygous condition for ß-thalassemia mutation associated with an extra functional α-globin gene can produce a Thalassemia Intermedia (TI) phenotype. This genotype is the second in frequency in the French Thalassemia Registry NaThalY that prospectively collects laboratory and clinical data. MATERIALS AND METHODS: The present report analyses transfusion needs, iron overload (ferritin, hepatic and cardiac iron concentrations), and complication rates in 45 patients included in NaThalY and presenting a heterozygous ß0 or ß+ -thalassemia mutation associated with a triplication at HBA locus. This cohort was compared to a cohort of patients with TI due to mutations in the beta-globin gene only and included in the French registry. RESULTS: Patients with an extra functional α-globin gene showed a less severe anemia, lower transfusion needs and lower complication rates than those with TI related to the ß-globin gene only. Nevertheless, some of them displayed complications such as cholelithiasis or extramedullary hematopoiesis. In addition, one third of the cohort needed transfusions and another third was under iron chelation. CONCLUSION: The genotype associating a heterozygous ß0 or ß+ -thalassemia mutation with a triplication at HBA locus should be accurately diagnosed as it could lead to symptomatic anemia and to potential iron overload and iron-related complications even in patients with no transfusion need.

Clinical and electrophysiological characteristics of women with X-linked Charcot-Marie-Tooth disease.

BACKGROUND: X-Linked Charcot-Marie-Tooth disease type 1 (CMTX1) is characterized by gender differences in clinical severity. Women are usually clinically affected later and less severely than men. However, their clinical presentation appears to be heterogenous. Our aim was to extend the phenotypic description in a large series of women with CMTX1. METHODS: We retrospectively evaluated 263 patients with CMTX1 from 11 French reference centers. Demographic, clinical, and nerve conduction data were collected. The severity was assessed by CMT Examination Score (CMTES) and Overall Neuropathy Limitations Scale (ONLS) scores. We looked for asymmetrical strength, heterogeneous motor nerve conduction velocity (MNCV), and motor conduction blocks (CB). RESULTS: The study included 137 women and 126 men from 151 families. Women had significantly more asymmetric motor deficits and MNCV than men. Women with an age of onset after 19 years were milder. Two groups of women were identified after 48 years of age. The first group represented 55%, with women progressing as severely as men, however, with a later onset age. The second group had mild or no symptoms. Some 39% of women had motor CB. Four women received intravenous immunoglobulin before being diagnosed with CMTX1. CONCLUSIONS: We identified two subgroups of women with CMTX1 who were over 48 years of age. Additionally, we have demonstrated that women with CMTX can exhibit an atypical clinical presentation, which may result in misdiagnosis. Therefore, in women presenting with chronic neuropathy, the presence of clinical asymmetry, heterogeneous MNCV, and/or motor CB should raise suspicion for X-linked CMT, particularly CMTX1, and be included in the differential diagnosis.

SORD-related peripheral neuropathy in a French and Swiss cohort: Clinical features, genetic analyses, and sorbitol dosages.

BACKGROUND AND PURPOSE: Biallelic variants in SORD have been reported as one of the main recessive causes for hereditary peripheral neuropathies such as Charcot-Marie-Tooth disease type 2 (CMT2) and distal hereditary motor neuropathy (dHMN) resulting in lower limb (LL) weakness and muscular atrophy. In this study, phenotype and genotype landscapes of SORD-related peripheral neuropathies were described in a French and Swiss cohort. Serum sorbitol dosages were used to classify SORD variants. METHODS: Patients followed at neuromuscular reference centres in France and Switzerland were ascertained. Sanger sequencing and next generation sequencing were performed to sequence SORD, and mass spectrometry was used to measure patients' serum sorbitol. RESULTS: Thirty patients had SORD peripheral neuropathy associating LL weakness with muscular atrophy, foot deformities (87%), and sometimes proximal LL weakness (20%) or distal upper limb weakness (50%). Eighteen had dHMN, nine had CMT2, and three had intermediate CMT. Most of them had a mild or moderate disease severity. Sixteen carried a homozygous c.757delG (p.Ala253Glnfs*27) variant, and 11 carried compound heterozygous variants, among which four variants were not yet reported: c.403C > G, c.379G > A, c.68_100 + 1dup, and c.850dup. Two unrelated patients with different origins carried a homozygous c.458C > A variant, and one patient carried a new homozygous c.786 + 5G > A variant. Mean serum sorbitol levels were 17.01 mg/L ± 8.9 SD for patients carrying SORD variants. CONCLUSIONS: This SORD-inherited peripheral neuropathy cohort of 30 patients showed homogeneous clinical presentation and systematically elevated sorbitol levels (22-fold) compared to controls, with both diagnostic and potential therapeutic implications.

Co-occurrence of oculocutaneous albinism type 2 and mild sickle cell disease explained by HbS/ßthal genotype in an individual from the Democratic Republic of Congo.

Oculocutaneous albinism type 2 (OCA2) is a pigmentation disorder characterized by hypopigmentation of the skin, hair and eyes and ocular features. Sickle cell disease (SCD) is caused either by homozygosity of the beta globin gene variant c.20A > T/p.Glu6Val giving rise to severe anemia or by combined abnormal hemoglobins (HbS/ßthal) leading to mild SCD. We report a 45 years old female patient from the Democratic Republic of Congo affected with these two disorders. She presented with creamy white skin and numerous pigmented patches called dendritic freckles, nystagmus, foveal hypoplasia grade 2, photophobia and very poor visual acuity. Sequencing of the OCA2 gene identified the common exon 7 deletion and a new pathogenic variant c.1444A > C/p.Thr482Pro. She had mild SCD with a total Hb level of 101 g/l. Hbß sequencing identified variants c.20A > T giving rise to HbS and c.315 + 1 G > A characteristic of ß-thalassemia. A heterozygous 3.7 kb deletion of the α globin gene was also found. The combined Hbß/α globin genotype explains the mild SCD phenotype. Co-occurrence of OCA2 and SCD raises the question whether the patient's phenotype simply results from the addition of the two diseases' phenotypes or whether interaction between the two diseases modulates the phenotype of each other.

HINT1 neuropathy: Expanding the genotype and phenotype spectrum.

Inherited peripheral neuropathy (IPN) is a heterogeneous group of disorders due to pathogenic variation in more than 100 genes. In 2012, the first cases of IPN associated with HINT1 pathogenic variations were described in 33 families sharing the same phenotype characterized by an axonal neuropathy with neuromyotonia and autosomal recessive inheritance (NMAN: OMIM #137200). Histidine Triad Nucleotide Binding Protein 1 regulates transcription, cell-cycle control, and is possibly involved in neuropsychiatric pathophysiology. Herein, we report seven French patients with NMAN identified by Next Generation Sequencing. We conducted a literature review and compared phenotypic and genotypic features with our cohort. We identified a new HINT1 pathogenic variation involved in NMAN: c.310G>C p.(Gly104Arg). This cohort is comparable with literature data regarding age of onset (7,4yo), neuronal involvement (sensorimotor 3/7 and motor pure 4/7), and skeletal abnormalities (scoliosis 3/7, feet anomalies 6/7). We expand the phenotypic spectrum of HINT1-related neuropathy by describing neurodevelopmental or psychiatric features in six out of seven individuals such as generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), mood disorder and attention deficit hyperactivity disorder (ADHD). However, only 3/128 previously described patients had neuropsychiatric symptomatology or neurodevelopmental disorder. These features could be part of HINT1-related disease, and we should further study the clinical phenotype of the patients.

A National French Consensus on Gene List for the Diagnosis of Charcot-Marie-Tooth Disease and Related Disorders Using Next-Generation Sequencing.

Next generation sequencing (NGS) is strategically used for genetic diagnosis in patients with Charcot-Marie-Tooth disease (CMT) and related disorders called non-syndromic inherited peripheral neuropathies (NSIPN) in this paper. With over 100 different CMT-associated genes involved and ongoing discoveries, an important interlaboratory diversity of gene panels exists at national and international levels. Here, we present the work of the French National Network for Rare Neuromuscular Diseases (FILNEMUS) genetic diagnosis section which coordinates the seven French diagnosis laboratories using NGS for peripheral neuropathies. This work aimed to establish a unique, simple and accurate gene classification based on literature evidence. In NSIPN, three subgroups were usually distinguished: (1) HMSN, Hereditary Motor Sensory Neuropathy, (2) dHMN, distal Hereditary Motor Neuropathy, and (3) HSAN, Hereditary Sensory Autonomic Neuropathy. First, we reported ClinGen evaluation, and second, for the genes not evaluated yet by ClinGen, we classified them as "definitive" if reported in at least two clinical publications and associated with one report of functional evidence, or "limited" otherwise. In total, we report a unique consensus gene list for NSIPN including the three subgroups with 93 genes definitive and 34 limited, which is a good rate for our gene's panel for molecular diagnostic use.

Genotype-phenotype correlation in French patients with myelin protein zero gene-related inherited neuropathy.

BACKGROUND AND PURPOSE: Preparations for clinical trials of unfolded protein response (UPR) inhibitors (such as Sephin1) that target the upregulated UPR in patients with Charcot-Marie-Tooth disease (CMT) carrying MPZ mutations are currently underway. The inclusion criteria for these trials are still being formulated. Our objective was to characterize the relation between genotypes and phenotypes in patients with CMT caused by MPZ mutations, and to refine the inclusion criteria for future trials. METHODS: Clinical and neurophysiological data of CMT patients with MPZ mutations were retrospectively collected at 11 French reference centers. RESULTS: Forty-four mutations in MPZ were identified in 91 patients from 61 families. There was considerable heterogeneity. The same mutation was found to cause either axonal or demyelinating neuropathy. Three groups were identified according to the age at disease onset. CMT Examination Score (CMTES) tended to be higher in the early (≤22 years) and adult (23-47 years) onset groups (mean CMTESv2 = 10.4 and 10.0, respectively) than in the late onset group (>47 years, mean CMTESv2 = 8.6, p = 0.47). There was a significant positive correlation between CMTESv2 and the age of patients in Groups I (p = 0.027) and II (p = 0.023), indicating that clinical severity progressed with age in these patients. CONCLUSIONS: To optimize the selection of CMT patients carrying MPZ mutations for the upcoming trials, inclusion criteria should take into account the pathophysiology of the disease (upregulated UPR). Recruited patients should have a mild to moderate disease severity and a disease onset at between 18 and 50 years, as these patients exhibit significant disease progression over time.

Retrospective analysis and reclassification of DYSF variants in a large French series of dysferlinopathy patients.

PURPOSE: Recent evolution of sequencing technologies and the development of international standards in variant interpretation have profoundly changed the diagnostic approaches in clinical genetics. As a consequence, many variants that were initially claimed to be disease-causing can be now reclassified as benign or uncertain in light of the new data available. Unfortunately, the misclassified variants are still present in the scientific literature and variant databases, greatly interfering with interpretation of diagnostic sequencing results. Despite the urgent need, large-scale efforts to update the classifications of these variants are still not sufficient. METHODS: We retrospectively analyzed 176 DYSF gene variants that were identified in dysferlinopathy patients referred to the Marseille Medical Genetics Department for diagnostic sequencing since 2001. RESULTS: We reclassified all variants into five-tier American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) pathogenicity classes, revealing changed pathogenicity for 17 variants. We then updated the information for the variants that have been previously published in the variant database and submitted 46 additional DYSF variants. CONCLUSION: Besides direct benefit for dysferlinopathy diagnostics, our study contributes to the much needed effort to reanalyze variants from previously published cohorts and to work with curators of variant databases to update the entries for erroneously classified variants.

A Rare Mutation in LMNB2 Associated with Lipodystrophy Drives Premature Cell Senescence.

Many proteins are causative for inherited partial lipodystrophies, including lamins, the essential constituents of the nuclear envelope scaffold called the lamina. By performing high throughput sequencing on a panel of genes involved in lipodystrophies, we identified a heterozygous mutation in LMNB2 gene (c.700C > T p.(Arg234Trp)) in a female patient presenting early onset type II diabetes, hypertriglyceridemia, and android fat distribution. This mutation is rare in the general population (frequency 0.013% in GnomAD) and was predicted pathogenic by a set of pathogenicity prediction software. Patient-derived fibroblasts showed nuclear shape abnormalities and premature senescence features, which are two typical cellular phenotypes associated with laminopathies. Moreover, we observed an atypical aggregation of lamin B2 in nucleoplasm, which co-distributes with emerin and lamin A/C, along with an abnormal distribution of lamin A/C at the nuclear envelope. Finally, reducing lamin B2 expression level by siRNA targeted toward LMNB2 transcripts resulted in decreased nuclear anomalies and senescence-associated beta-galactosidase, suggesting a role of the mutated protein in the occurrence of the observed cellular phenotype. Altogether, these results suggest that mutations in lamin B2 could produce premature senescence and partial lipodystrophy features as observed with certain mutants of lamin A/C.

HbF-promoting polymorphisms may specifically reduce the residual risk of cerebral vasculopathy in SCA children with alpha-thalassemia.

Sickle cell anemia (SCA) is a disease characterized by abnormal red blood cell rheology. Because of their effects on HbS polymerization and red blood cell deformability, alpha-thalassemia and the residual HbF level are known genetic modifiers of the disease. The aim of our study was to determine if the number of HbF quantitative trait loci (QTL) would also favor a specific sub-phenotype of SCA as it is the case for alpha-thalassemia. Our results confirmed that alpha-thalassemia protected from cerebral vasculopathy but increased the risk for frequent painful vaso-occlusive crises. We also showed that more HbF-QTL may provide an additional and specific protection against cerebral vasculopathy but only for children with alpha-thalassemia (-α/αα or -α/-α genotypes).

Three Mexican Families with ß thalassemia intermedia with different molecular basis.

Beta thalassemia (ß-thal) is a frequent monogenic disease, is clinically and molecularly heterogeneous. This study described molecular and laboratory findings for three Mexican patients with ß-thal intermedia phenotype and their relatives. Three Mexican families were studied for presenting ß-thal intermedia, ARMS-PCR and Gap-PCR were performed to screen for common mutations, Sanger sequencing for rare or new alleles, and MLPA for identifying deletions and or duplications. In all three families we observed, in heterozygote condition, the mutation c.118C > T (p.Gln39*) also known as codon 39(C > T) in the ß globin gene (HBB) associated with a novel molecular defect: a new duplication of the alpha globin gene cluster, a new deletion that includes the loss of exon 3 of HBB and finally a novel mutation in the 3'UTR of HBB (HBB: c.*132C > A). We report three Mexican families with beta thalassemia intermedia due to different molecular basis; a new single nucleotide mutation involving the last nucleotide of the ß-globin chain transcript; and two possible new DNA rearrangements, an α cluster duplication, and a partial ß gene deletion.

Unraveling LMNA Mutations in Metabolic Syndrome: Cellular Phenotype and Clinical Pitfalls.

This study details the clinical and cellular phenotypes associated with two missense heterozygous mutations in LMNA, c.1745G > T p.(Arg582Leu), and c.1892G> A p.(Gly631Asp), in two patients with early onset of diabetes mellitus, hypertriglyceridemia and non-alcoholic fatty liver disease. In these two patients, subcutaneous adipose tissue was persistent, at least on the abdomen, and the serum leptin level remained in the normal range. Cellular studies showed elevated nuclear anomalies, an accelerated senescence rate and a decrease of replication capacity in patient cells. In cellular models, the overexpression of mutated prelamin A phenocopied misshapen nuclei, while the partial reduction of lamin A expression in patient cells significantly improved nuclear morphology. Altogether, these results suggest a link between lamin A mutant expression and senescence associated phenotypes. Transcriptome analysis of the whole subcutaneous adipose tissue from the two patients and three controls, paired for age and sex using RNA sequencing, showed the up regulation of genes implicated in immunity and the down regulation of genes involved in development and cell differentiation in patient adipose tissue. Therefore, our results suggest that some mutations in LMNA are associated with severe metabolic phenotypes without subcutaneous lipoatrophy, and are associated with nuclear misshaping.

High prevalence of mutations in perilipin 1 in patients with precocious acute coronary syndrome.

BACKGROUND AND AIMS: Genetic partial lipodystrophies are rare heterogeneous disorders characterized by abnormalities of fat distribution and associated metabolic complications including a predisposition for atherosclerotic cardiovascular disease. We hypothesized that the milder forms of these diseases might be underdiagnosed and might result in early acute coronary syndrome (ACS) as the first sign of the pathology. METHODS: We performed targeted sequencing on a panel of 8 genes involved in genetic lipodystrophy for 62 patients with premature ACS, and selected heterozygous missense variations with low frequency. To confirm those results, we analyzed a second independent group of 60 additional patients through Sanger sequencing, and compared to a control group of 120 healthy patients. RESULTS: In the first cohort, only PLIN1 exhibited variants in more than 1 patient. In PLIN1, 3 different variants were found in 6 patients. We then analyzed PLIN1 sequence in the second cohort with premature ACS and found 2 other patients. Altogether, 8 patients were carriers of 4 different mutations in PLIN1. The variant frequencies in the total cohort of 122 patients were compared to frequencies observed in a local control cohort and in 2 different public databases showing a significant difference between patient vs control group frequencies for two mutations out of 4 (c.245C > T p = 10-4; c.839G > A p = 0.014). DISCUSSION: This is the first study that identifies a high frequency of potential pathogenic mutations in PLIN1 related to early onset ACS. These findings could contribute to the prevention and care of precocious ACS in families carrying those mutations.

Hereditary sensory autonomic neuropathy type II: Report of two novel mutations in the FAM134B gene.

Hereditary sensory autonomic neuropathy (HSAN) type II is a rare, autosomal recessive, and early onset sensory neuropathy, characterized by severe and progressive sensation impairment, leading to ulcero-mutilating complications. FAM134B gene, also known as RETREG1 gene, mutations have been reported to be associated to HSAN-IIB. We report four patients from two unrelated families who developed during childhood a sensory axonal neuropathy with variable severity and pronounced nociception impairment. Complications such as recurrent ulcerations, osteomyelitis, and osteonecrosis leading to distal amputation were noticed. Dysautonomia was mild or even absent in our group of patients. Additionally, either clinical or neurophysiological motor impairment was not uncommon. Presence of upper motor neuron signs was also a distinctive feature in two related patients. After extensive workup, two novel homozygous mutations in the FAM134B gene were identified. This report expands the clinical and genetic spectrum of HSAN type II and emphasizes the phenotype variability even within the same family.

A multicenter retrospective study of charcot-marie-tooth disease type 4B (CMT4B) associated with mutations in myotubularin-related proteins (MTMRs).

OBJECTIVE: Charcot-Marie-Tooth (CMT) disease 4B1 and 4B2 (CMT4B1/B2) are characterized by recessive inheritance, early onset, severe course, slowed nerve conduction, and myelin outfoldings. CMT4B3 shows a more heterogeneous phenotype. All are associated with myotubularin-related protein (MTMR) mutations. We conducted a multicenter, retrospective study to better characterize CMT4B. METHODS: We collected clinical and genetic data from CMT4B subjects in 18 centers using a predefined minimal data set including Medical Research Council (MRC) scores of nine muscle pairs and CMT Neuropathy Score. RESULTS: There were 50 patients, 21 of whom never reported before, carrying 44 mutations, of which 21 were novel and six representing novel disease associations of known rare variants. CMT4B1 patients had significantly more-severe disease than CMT4B2, with earlier onset, more-frequent motor milestones delay, wheelchair use, and respiratory involvement as well as worse MRC scores and motor CMT Examination Score components despite younger age at examination. Vocal cord involvement was common in both subtypes, whereas glaucoma occurred in CMT4B2 only. Nerve conduction velocities were similarly slowed in both subtypes. Regression analyses showed that disease severity is significantly associated with age in CMT4B1. Slopes are steeper for CMT4B1, indicating faster disease progression. Almost none of the mutations in the MTMR2 and MTMR13 genes, responsible for CMT4B1 and B2, respectively, influence the correlation between disease severity and age, in agreement with the hypothesis of a complete loss of function of MTMR2/13 proteins for such mutations. INTERPRETATION: This is the largest CMT4B series ever reported, demonstrating that CMT4B1 is significantly more severe than CMT4B2, and allowing an estimate of prognosis. ANN NEUROL 2019.