Pituitary leptin gene expression is reduced by neonatal androgenization of female rats.

We have previously reported evidence of leptin gene expression (ob mRNA) in adult rat brain and pituitary gland. We have also shown that ob mRNA levels in female rat brain and pituitary are regulated in an age- and tissue-dependent fashion. In view of the known sexual dimorphism in adipose tissue leptin expression, we have extended our original work to include an assessment of ob mRNA levels in brain, pituitary and fat of developing male and female rats. In addition we determined the effects of neonatal androgenization of female rat pups with testosterone propionate. Leptin (ob) mRNA expression was evaluated using semi-quantitative RT-PCR analysis. Leptin mRNA levels were developmentally regulated in the pituitary and cortex of male rats, paralleling the changes previously observed in female rats. In the pituitary, leptin expression was significantly higher during the early postnatal period and dropped abruptly by postnatal day (PD) 22. In the cortex, leptin expression was lowest at PD 4 and rose significantly by PD 14. In addition gender differences, most notably in the pituitary, were also observed. In pituitary gland, ob mRNA was significantly higher in female rats than in males at PD 14 (+60%; p < 0.05) but there were no sex differences at PD 4 and PD 22. Testosterone treatment of neonatal female rats profoundly reduced ob mRNA at PD 14 (3.5-fold; p < 0.01) and PD 22 (3-fold; p = 0.05). In subcutaneous adipose tissue and hypothalamus we observed no sex difference in ob mRNA levels nor an effect of testosterone. We conclude that leptin gene expression in rat pituitary gland is sexually dimorphic and sensitive to neonatal manipulation of sex steroid levels.

A novel mutation in Exon 4 of the low density lipoprotein receptor gene resulting in heterozygous familial hypercholesterolemia associated with decreased ligand binding.

Familial hypercholesterolemia (FH) is an autosomal dominant disorder caused by mutations in the low density lipoprotein (LDL) receptor gene. Currently, diagnosis of heterozygous FH relies on clinical phenotype; however, the use of clinical criteria for the diagnosis of heterozygous FH does not always permit unequivocable diagnosis of the disease. Molecular diagnosis of FH is clinically valuable especially in regions where founder mutations exist or where polygenic hypercholesterolemia is prevalent. In this paper we report the identification of a novel mutation, a cytosine to guanine substitution, at codon 152 in exon 4 of the LDL receptor gene in a Nova Scotian family clinically diagnosed with heterozygous FH. The mutation creates a recognition sequence for the restriction endonuclease BsrI, and can be readily detected by BsrI restriction analysis of a 160 bp amplicon spanning the mutation. This analysis was used to show that the mutation segregated with the disease in this family and is the probable cause of FH in this kindred.

Establishment and characterization of a renal cell carcinoma line from a patient with von Hippel-Lindau syndrome.

It is not known how the von Hippel-Lindau (VHL) gene and the, as yet unidentified, renal cell carcinoma (RCC) gene(s) interact to result in RCC; nor is it known if mutations in both, or all genes are necessary for this progression. The availability of a RCC cell line from a VHL patient would be useful in studies comparing sporadic RCC with RCC resulting from VHL syndrome; and for determining the relationship or interaction of the RCC gene with the VHL gene to produce a common tumor type. This paper describes the isolation and characterization of a renal cell carcinoma cell line derived from a patient with von Hippel-Lindau disease. The line is epithelial in origin and the genome contains a familial mutation in the VHL gene. Tissue culture studies indicate that this cell line, although immortalized, is not fully transformed. Chromosomal analysis performed on cells derived from disseminated primary tumor cells revealed no detectable chromosomal abnormalities. However, analysis performed on cells at passages 9, 19, 41, and 79 showed both numerical and structural chromosomal changes. The cytogenetic profile of this cell line demonstrated a number of abnormalities known to be associated with RCC from patients with and without VHL syndrome.