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Mutations in Gng3lg and AGPAT2 in Berardinelli-Seip congenital lipodystrophy and Brunzell syndrome: phenotype variability suggests important modifier effects.

ABSTRACT: Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder caused by mutations in AGPAT2 and Gng3lg. We screened for mutations in AGPAT2 and Gng3lg in 26 families with CGL and one family with Brunzell syndrome. We found mutations in either AGPAT2 or Gng3lg in all but four probands, including three novel mutations in AGPAT2, A712T (Lys215X), IVS3-1G-->C, and C636A (Phe189X). In three siblings with Brunzell syndrome, we identified a splice site mutation (IVS4-2A-->G) in AGPAT2, showing that AGPAT2 mutations can also cause Brunzell syndrome. Eighteen CGL patients from 15 families from the same region of northeastern Brazil were homozygous for a frameshift mutation (669insA of AF05149) in Gng3lg. Despite having the same mutation, the subjects had widely divergent clinical manifestations. In our subjects, there did not appear to be any distinguishing clinical characteristics between CGL subjects with AGPAT2 or Gng3lg mutations with the exception of mental retardation in carriers of Gng3lg. In summary, mutations in AGPAT2 and Gng3lg are approximately equally represented in CGL; despite harboring the same Gng3lg mutation, subjects may have widely divergent clinical manifestations, suggesting modifying influences of other genes and/or environment; and Brunzell syndrome may be caused by a mutation in AGPAT2.

SUBMITTER: Fu M

PROVIDER: S-EPMC3390418 | biostudies-literature | 2004 Jun

REPOSITORIES: biostudies-literature

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Mutations in Gng3lg and AGPAT2 in Berardinelli-Seip congenital lipodystrophy and Brunzell syndrome: phenotype variability suggests important modifier effects.

Fu Mao M Kazlauskaite Rasa R Baracho Maria de Fátima Paiva Mde F Santos Maria Goretti Do Nascimento MG Brandão-Neto José J Villares Sandra S Celi Francesco S FS Wajchenberg Bernardo L BL Shuldiner Alan R AR

The Journal of clinical endocrinology and metabolism 20040601 6

Congenital generalized lipodystrophy (CGL) is a rare autosomal recessive disorder caused by mutations in AGPAT2 and Gng3lg. We screened for mutations in AGPAT2 and Gng3lg in 26 families with CGL and one family with Brunzell syndrome. We found mutations in either AGPAT2 or Gng3lg in all but four probands, including three novel mutations in AGPAT2, A712T (Lys215X), IVS3-1G-->C, and C636A (Phe189X). In three siblings with Brunzell syndrome, we identified a splice site mutation (IVS4-2A-->G) in AGPA ...[more]

PMID: 15181077

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Project description:Berardinelli-Seip congenital lipodystrophy (BSCLD) (OMIM#269700) is a rare autosomal recessive disorder characterized by marked paucity of adipose tissue, a muscular habitus, insulin resistance, hypertriglyceridemia and hepatic steatosis. It is an anabolic syndrome due to the deficiency of leptin, a lipid modulator, leading to the inappropriate mobilization of fat. Four types of BSCLD have been described based on the site of genetic mutation. Type 2 accounts for an earlier onset, more severe complications and intellectual disability. This is due to the lower leptin levels and the loss of functional seipin in type 2 BSCLD. We report the evolving phenotype of type 2 BSCLD in a boy clinically diagnosed at age 5 months and confirmed by molecular genetic study which revealed a pathogenic mutation in the BSCL2 gene: c.782dupG, p.lle262Hisfs*12homozygous. He is the firstborn of non-consanguineous parents with no significant family history. He has a muscular habitus with a distinct facies, hypertrichosis, absence of subcutaneous fat and hepatomegaly. Investigations revealed hypertriglyceridemia and insulin resistance. A conventional approach to management with dietary fat restriction successfully controlled his biochemical parameters, thus preventing catastrophic complications such as systemic arterial hypertension, heart failure and pancreatitis. Genetic counseling was conferred and prenatal testing recommended for future pregnancies. On follow-up, he had a muscular habitus with hepatomegaly and global developmental delay. Despite early correction of his biochemical parameters, an abdominal ultrasound revealed early onset fatty liver disease and an echocardiogram showed a thickened interventricular septum suggestive of early hypertrophic obstructive cardiomyopathy (HOCM). A fasting serum leptin done was low at 0.8 ng/mL (normal range, 2.0-5.6 ng/mL) confirming leptin deficiency. A leptin analog is now available as an adjunct to mollify the metabolic complications of BSCLD. However, it is yet to be available in developing nations and whether it is able to assuage progressive hepatic cholestasis and HOCM remains a field to venture. This report highlights the importance of early recognition and confirmation by molecular diagnosis to direct appropriate surveillance of complications. This also enables early genetic counseling and prenatal testing for future pregnancies. We describe the evolving phenotype, pertinent investigations and the conventional approach to the management of BSCLD.

Project description:ObjectiveUnderstanding the mechanisms that control brown adipose tissue (BAT) mass and functionality is crucial for our understanding of how the disruption of energy homeostasis leads to obesity. Bernerdinali Seip Congenital Lipodystrophy (BSCL) type 2 (BSCL2, a.k.a. SEIPIN), a lipodystrophy-associated protein, has been shown to not be required for brown adipogenesis, but it has been shown to be essential for perinatal BAT development. However, its role in mature BAT maintenance and thermogenic programing remains poorly understood.MethodsWe subjected Bscl2f/f and Bscl2UCP1-BKO (BKO) mice with a brown adipose-specific loss of BSCL2 through UCP1 promoter-driven Cre to environmental, pharmacological and diet interventions to challenge BAT functionality and reprogramming. We carried out physiological, molecular and transcriptomic analyses of BAT.ResultsThe deletion of BSCL2 in mature brown adipocytes increased sympathetic nervous system-independent cAMP/protein kinase A (PKA) signaling in BAT. Such activation reduced BAT triglyceride content and mass and was sufficient to reduce plasma triglyceride, but not enough to combat thermoneutral and high fat diet-induced obesity. Surprisingly, BKO mice displayed an impaired response to acute and chronic cold challenges despite cAMP/PKA activation. When subjected to chronic cold exposure or the administration of a β3-adrenergic agonist, CL 316,243, BKO mice failed to induce BAT recruitment and underwent dramatic brown adipocyte loss. Transcriptomic analysis revealed pathological BAT remodeling with inflammation and fibrosis, which was further exacerbated by a chronic thermogenic challenge in BKO mice. Mechanistically, we found abnormal mitochondrial shapes and function in BAT of BKO mice housed at 21 °C; as well as mitochondrial DNA depletion and necroptotic-mediated brown adipocyte death after chronic thermogenic insult.ConclusionBSCL2-mediated lipid catabolism within BAT is crucial for mature brown adipocyte function and survival both during times of activation and quiescence. BSCL2 is an important regulator of mature brown adipocyte mitochondrial metabolism, necroptosis and thus adaptive thermogenesis.

Dataset Information

Mutations in Gng3lg and AGPAT2 in Berardinelli-Seip congenital lipodystrophy and Brunzell syndrome: phenotype variability suggests important modifier effects.

Publications

Mutations in Gng3lg and AGPAT2 in Berardinelli-Seip congenital lipodystrophy and Brunzell syndrome: phenotype variability suggests important modifier effects.

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