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.

A Heterozygous ZMPSTE24 Mutation Associated with Severe Metabolic Syndrome, Ectopic Fat Accumulation, and Dilated Cardiomyopathy.

ZMPSTE24 encodes the only metalloprotease, which transforms prelamin into mature lamin A. Up to now, mutations in ZMPSTE24 have been linked to Restrictive Dermopathy (RD), Progeria or Mandibulo-Acral Dysplasia (MAD). We report here the phenotype of a patient referred for severe metabolic syndrome and cardiomyopathy, carrying a mutation in ZMPSTE24. The patient presented with a partial lipodystrophic syndrome associating hypertriglyceridemia, early onset type 2 diabetes, and android obesity with truncal and abdominal fat accumulation but without subcutaneous lipoatrophy. Other clinical features included acanthosis nigricans, liver steatosis, dilated cardiomyopathy, and high myocardial and hepatic triglycerides content. Mutated fibroblasts from the patient showed increased nuclear shape abnormalities and premature senescence as demonstrated by a decreased Population Doubling Level, an increased beta-galactosidase activity and a decreased BrdU incorporation rate. Reduced prelamin A expression by siRNA targeted toward LMNA transcripts resulted in decreased nuclear anomalies. We show here that a central obesity without subcutaneous lipoatrophy is associated with a laminopathy due to a heterozygous missense mutation in ZMPSTE24. Given the high prevalence of metabolic syndrome and android obesity in the general population, and in the absence of familial study, the causative link between mutation and phenotype cannot be formally established. Nevertheless, altered lamina architecture observed in mutated fibroblasts are responsible for premature cellular senescence and could contribute to the phenotype observed in this patient.

Analytical evaluation of the Tosoh HLC-723 G8 automated HPLC analyzer for hemoglobin analysis in beta-thalassemia mode.

OBJECTIVES: The analytical performances of a new kit conceived for Hb variants separation and measurement procedures on an HPLC instrument (Tosoh HLC-723 G8) were studied. RESULTS: Between-run and within-run precision tests were satisfactory for both HbA2 and HbF measurements. HbA2 and HbF values measured using the TOSOH HLC-723 G8 were correlated to those obtained using the Bio-Rad Variant II HPLC system (r=0.974 and 0.997 respectively) and to those given by the Sebia Capillary's system (r=0.980 and 0.996 respectively). Linearity was observed for HbA2 from 2.24% to 6.56% and for HbF from 0.5 to 6%. CONCLUSION: The new analyzer Tosoh HLC-723 G8 was found to have a wide analytical range for both HbA2 and HbF. The G8 Mode beta-thal is suitable for a first-level laboratory screening for Hb analysis but also for a second-level test for the characterization of Hb variants after a first-line screening.

Neonatal screening for sickle cell disease in France: evaluation of the selective process.

AIMS: The French national programme for neonatal screening of sickle cell disease is applied to newborns 'at risk', defined as those born to parents originating from sub-Saharan Africa, the Mediterranean area, the Arabic peninsula, the French overseas islands and the Indian subcontinent. The selection is performed by the nurse in charge of blood sampling by interviewing the mother about the family's geographical origins. The mean rate of testing in France is 25%, ranging from 2% to 50% depending on the region. This study aimed to evaluate the effectiveness of selection during this screening programme. METHODS: False-negative cases were identified using two different approaches: first, a regional prospective study aimed at screening all newborns, selected and non-selected, in a restricted area, representing 3% of national births; second, a retrospective national survey to identify false-negative cases. RESULTS: The regional study indicated that selective screening leads to a carrier frequency that is twice as high in the selected population as compared with the non-selected population (1.23% versus 0.62%). The local and national surveys revealed that, during a 6-year period, 28 affected children failed to be selected, leading to a false-negative rate of 2.1%. In contrast to what was expected, most of the cases were due to the failing of the data collection process and not to the misdiagnosis of the risk. CONCLUSIONS: These results show that selective neonatal screening for sickle cell disease is feasible if very careful attention is paid to the selective step.