Functional characterization of variants in MC4R gene promoter region found in obese children.

CONTEXT: Mutations in the MC4R gene are the most common cause of monogenic obesity, and there are few studies on mutations in the promoter region. OBJECTIVE: The objective of the study was to sequence the promoter region of the MC4R gene in a cohort of obese children to identify rare variants. DESIGN, SETTING, AND PATIENTS: A region 1500 bp upstream of the MC4R gene was sequenced in 267 unrelated local children younger than 10 years, with body weight of at least 150% of ideal. An 891-bp upstream region of the MC4R gene was cloned into a luciferase reporter vector for reporter gene assays. INTERVENTIONS: There were no interventions. MAIN OUTCOME MEASURES: The basal transcriptional activity of the MC4R promoter was analyzed in human embryonic kidney 293 cells using reporter gene assays. RESULTS: Three rare variants were detected: c.-803A>G, c.-105C>G, and c.-216C>T. The novel c.-803A>G variant was found in a 9-year-old severely obese Malay boy. This variant was not found in his severely obese mother but was present in his overweight father, who had type 2 diabetes, and also in his normal-weight brother. The novel c.-105C>G variant was found in an obese 9-year-old Malay boy. The c.-216C>T variant was found in an obese Chinese girl with Down's syndrome. The transcriptional activities of the c.-803A>G and c.-105C>G promoters were significantly reduced compared with the wild type but not the c.-216C>T promoter. CONCLUSIONS: We have described, for the first time, two novel human MC4R gene promoter variants found in obese children that resulted in a decrease in basal transcriptional activity.

Familial male-limited precocious puberty in neurofibromatosis type I.

UNLABELLED: Precocious puberty in patients with neurofibromatosis type 1 (NF-1) is predominantly central in origin, with intracranial pathologies like optic glioma. We describe one patient with NF-1 who presented with precocious puberty with the eventual diagnosis of familial male-limited precocious puberty and share the potential pitfalls. He presented at 7 years of age with growth spurt and pubertal genitalia development with enlarged testicular volume of 7 mL, but LHRH stimulation test revealed blunted luteinizing hormone and follicle-stimulating hormone peak suggestive of a peripheral cause, contrary to the expectation due to the background of NF-1. Testosterone level was elevated with bone age advancement by 2 years. Genetic analysis revealed a previously reported heterozygous missense mutation of the luteinizing hormone/choriogonadotropin receptor gene Ala572Val. His father was also heterozygous for the same mutation but was apparently asymptomatic and not short. CONCLUSION: Our report illustrates two potential pitfalls in the clinical evaluation of patients with familial male-limited precocious puberty (FMPP). Firstly, patients with FMPP will have mild to moderately enlarged testes and should not be wrongly diagnosed as central precocious puberty without the gonadotropin-releasing hormone stimulation test. Secondly, family members with the same mutation may have different phenotypic severities, where some male carriers may have subtle features.

The association of a nucleobindin 2 gene (NUCB2) variant with childhood adiposity.

Nucleobindin 2 (NUCB2) is a precursor of nesfatin-1, a hypothalamic anorectic neuropeptide. The association between variants of the NUCB2 gene and adiposity was examined. 142 severely obese Chinese children in Singapore, and 384 normal weight Chinese children from a longitudinal cohort from Da Qing, China, were studied. NUCB2 was screened using PCR and direct sequencing in 29 severely obese children and 24 non-obese children, then screened for a variant c.1012C>G (Q338E, or rs757081) in the rest of the cohort using TaqMan probe. Five variants, including c.1012C>G (Q338E) were found. Genotyping for c.1012C>G found that the GG genotype was significantly less frequent in the obese group; odds ratio for obese subjects carrying the CC and CG genotypes was 2.29 (95% CI 1.17-4.49) in the dominant model, CC genotype 2.86 (95% CI 1.41-5.81) in the additive model, and C allele 1.57 (95% CI 1.17-2.1). The findings were replicated in an independent cohort of 372 obese and 390 normal weight Chinese children, where the odds ratio of obese subjects with CC and CG genotypes was 1.69 (95% CI 1.12-2.55). Within the Da Qing cohort, subjects with the GG genotype had significantly lower BMI and percentage ideal weight for height (WFH) at 5 and 8years of age. Subjects with lower birth weights also had more pronounced difference in WFH and BMI at 5 and 10years of age between GG subjects versus CC/CG subjects. We postulate that GG genotype is protective against excessive weight gain, and factors which predispose to excessive weight gain such as higher birth weights may ameliorate the effect.