Identification of the gene altered in Berardinelli-Seip congenital lipodystrophy on chromosome 11q13.

Congenital generalized lipodystrophy, or Berardinelli-Seip syndrome (BSCL), is a rare autosomal recessive disease characterized by a near-absence of adipose tissue from birth or early infancy and severe insulin resistance. Other clinical and biological features include acanthosis nigricans, hyperandrogenism, muscular hypertrophy, hepatomegaly, altered glucose tolerance or diabetes mellitus, and hypertriglyceridemia. A locus (BSCL1) has been mapped to 9q34 with evidence of heterogeneity. Here, we report a genome screen of nine BSCL families from two geographical clusters (in Lebanon and Norway). We identified a new disease locus, designated BSCL2, within the 2.5-Mb interval flanked by markers D11S4076 and D11S480 on chromosome 11q13. Analysis of 20 additional families of various ethnic origins led to the identification of 11 families in which the disease cosegregates with the 11q13 locus; the remaining families provide confirmation of linkage to 9q34. Sequence analysis of genes located in the 11q13 interval disclosed mutations in a gene homologous to the murine guanine nucleotide-binding protein (G protein), gamma3-linked gene (Gng3lg) in all BSCL2-linked families. BSCL2 is most highly expressed in brain and testis and encodes a protein (which we have called seipin) of unknown function. Most of the variants are null mutations and probably result in a severe disruption of the protein. These findings are of general importance for understanding the molecular mechanisms underlying regulation of body fat distribution and insulin resistance.

[Mitochondrial encephalopathy affecting only the central nervous system]. / Encéphalopathie mitochondriale avec atteinte exclusive du système nerveux central.

A 32 year-old diabetic woman presented with an acute coma followed by epileptic seizures, aphasia and constructive apraxia. No ischemic lesion was demonstrated by CT scan and carotid angiograms. The other investigations showed sensorineural hearing loss, retinal degeneration, calcifications of the basal ganglia and lactic acidosis. The follow-up was marked by pseudo-dementia with personality disorders, memory deficits, behavioural changes, migrainous and epileptic features. Although there was no sign of muscular deficiency, a muscular biopsy showed characteristic ragged-red fibers and mitochondrial abnormalities at electron microscopy. The muscular biopsy enables us to classify this case as a mitochondrial encephalopathy similar to the MELAS syndrome. The stroke-like episodes are probably caused by a specific angiopathy involving the mitochondria of brain vessels.

Long-term study of mortality and vascular complications in juvenile-onset (type I) diabetes.

A cohort of 372 insulin-dependent diabetic children, diagnosed between October 1949 and December 1960, were followed-up until December 1976 by the same team of physicians. At the time of diagnosis all patients were under 16 yr of age and were given standardized treatment which did not change from 1949 to 1976. The therapy consisted of daily insulin adjustment based on clinical assessment, the degree of physical activity, and the results of semi-quantitative urine tests for sugar and ketone bodies. These tests were systematically performed before breakfast, lunch, and dinner. Diet was normal, unmeasured, rich in carbohydrates (approximately 60%), and quantitatively unrestricted unless the patient was overweight. Rates for mortality and for the principal complications among this cohort were computed by the actuarial method. During the 26 yr of study, 26 deaths occurred, 16 of which were directly connected with diabetes. After 16 yr of follow-up, rates of proteinuria and hypertension were 4% and 2.1% respectively. The incidence of retinopathy reached 27%, including 1.5% proliferative retinopathy. After 26 yr, the rates rose to 14% for proteinuria, 16% for hypertension, and 85% for retinopathy, including 18% in the proliferative phase.