Mutational Screening of the CART Gene in Obese Children

Abstract

Cocaine- and amphetamine-regulated transcript (CART) inhibits feeding and induces the expression of c-Fos in hypothalamic areas implicated in appetite regulation. Furthermore, the CART peptide is found in neurons regulating sympathetic outflow, which in turn play an integral role in regulating body temperature and energy expenditure. The CART gene was screened by single-strand conformation polymorphism and automatic sequencing in 130 (72 girls) unrelated obese Italian children and adolescents. Their Z-scores (mean +/- SD) of relative to BMI percentiles was 3.9 +/- 1.8, and the average age at obesity onset was 4.7 +/- 2.6 years. Two previously described silent polymorphisms were found in the 3' untranslated region: an adenine deletion at position 1457 in 9 patients (allele frequency 0.035) and an A/G substitution at position 1475 in 11 patients (allele frequency 0.042). We found no difference between the obese patients heterozygous for one of these polymorphisms and those patients homozygous for the wild allele with respect to their age of obesity onset, BMI Z-scores, and leptin levels. A missense mutation of G729C resulting in the substitution of Leu with Phe at codon 34, within the NH2-terminal CART region, has been detected in the heterozygous state in a 10-year-old obese boy who has been obese since the age of 2 years. The patient belongs to a large family of obese subjects. The mutation cosegregated with the severe obesity phenotype over three generations and was not found in the control population. Resting metabolic rates were lower than expected in the propositus (-14%) and his mother (-16%), who carried the mutation. Leucine at codon 34, conserved in this position in the human and in the rat sequences, immediately precedes a couple of lysine residues that may well represent a dibasic processing site. The Leu34Phe mutation might alter the susceptibility to proteolysis of this potential processing site, likely altering the CART effect on thermogenesis and energy expenditure.

Molecular screening of the ghrelin gene in Italian obese children: the Leu72Met variant is associated with an earlier onset of obesity

“…Every cycle of the polymerase chain reaction (PCR) except the first one (961C for 4.30 min) was performed as follow: 961C for 30 s, 641C for 30 s and 721C for 30 s. The PCR products were screened using the single-strand conformation polymorphism (SSCP) analysis as previously described. 16 Two previously described polymorphisms, Arg51Gln (G152A) and Leu72Met (C214A), which could not be distinguished by SSCP, were directly detected by digesting the 278 bp fragment with AvaI (Arg51 allele: fragments of 168 and 110 bp) and BrsI (Leu72 allele: fragments of 172 and 106 bp). Restriction patterns were visualized on 2% agarose gels stained with ethidium bromide.…”

CART peptides as modulators of dopamine and psychostimulants and interactions with the mesolimbic dopaminergic system

“…Human genetic studies also support this hypothesis. A missense mutation has been associated with early onset obesity [48] and another mutation associates with increased weight [49] The issue of CART and body weight has been critically reviewed [44].…”

Controle neuroendócrino do peso corporal: implicações na gênese da obesidade

“…O RNAm do CART foi descoberto em 1995, quando a administração de estimulantes psicomotores induziu a expressão deste transcrito no SNC (87). Alguns estudos não demonstraram associação da obesidade a variantes do gene CART (87,88), mas um estudo identificou uma mutação associada à diminuição do gasto energético e à obesidade (89). O CRH, o TRH e a ocitocina, outros componentes da via anorexígena, estão localizados no núcleo paraventricular do hipotálamo, sendo estimulados pelos neurônios POMC/CART e inibidos pelos NPY/AGRP (4).…”