Browsing by Author "Carvajal, CA"

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    Biochemical and genetic characterization of 11 beta- hydroxysteroid dehydrogenase type 2 in low-renin essential hypertensives
    (LIPPINCOTT WILLIAMS & WILKINS, 2005) Carvajal, CA; Romero, DG; Mosso, LM; Gonzalez, AA; Campino, C; Montero, J; Fardella, CE
    Background The 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) catalyzes the conversion of cortisol M to cortisone (E), avoiding the interaction of cortisol with the mineralocorticoid receptor. If it fails, cortisol will stimulate sodium and water reabsorption, increasing the intravascular volume that suppresses renin and secondarily increase the blood pressure.
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    Congenital lipoid adrenal hyperplasia caused by a novel splicing mutation in the gene for the steroidogenic acute regulatory protein
    (ENDOCRINE SOC, 2004) Gonzalez, AA; Reyes, ML; Carvajal, CA; Tobar, JA; Mosso, LM; Baquedano, P; Solar, A; Venegas, A; Fardella, CE
    Steroidogenic acute regulatory protein (StAR) plays a crucial role in the transport of cholesterol from the cytoplasm to the inner mitochondrial membrane, facilitating its conversion to pregnenolone by cytochrome P450scc. Its essential role in steroidogenesis was demonstrated after observing that StAR gene mutations gave rise to a potentially lethal disease named congenital lipoid adrenal hyperplasia, in which virtually no steroids are produced. We report here a 2-month-old female patient, karyotype 46XY, who presented with growth failure, convulsions, dehydration, hypoglycemia, hyponatremia, hypotension, and severe hyperpigmentation suggestive of adrenal insufficiency. Serum cortisol, 17OH-progesterone, dehydroepiandrosterone sulfate, testosterone, 17OH-pregnenolone, and aldosterone levels were undetectable in the presence of high ACTH and plasma renin activity levels. Immunohistochemical analysis of testis tissues revealed the absence of StAR protein. Molecular analysis of StAR gene demonstrated a homozygous G to T mutation within the splice donor site of exon 1 (IVS1 + 1G>T). Her parents and one brother were heterozygous for this mutation. In vitro analysis of the mutation was performed in COS cells transfected with minigenes coding regions spanning exon-intron 1 to 3 carrying the mutant and the wild-type sequences. RT-PCR analyses of the mutant gene showed an abnormal mRNA transcript of 2430 bp (normal size 433 bp). Sequence analysis of the mutant mRNA demonstrated the retention of intron 1. Immunolocalization of the StAR minigene product detected the peptide in the mitochondria of COS cells transfected with the wild-type minigene but not in those transfected with the mutant minigene. We conclude that this mutation gives rise to a truncated StAR protein, which lacks an important N-terminal region and the entire lipid transfer domain.
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    Novel intronic mutation of MEN1 gene causing familial isolated primary hyperparathyroidism
    (ENDOCRINE SOC, 2004) Carrasco, CA; Gonzalez, AA; Carvajal, CA; Campusano, C; Oestreicher, E; Arteaga, E; Wohllk, N; Fardella, CE
    Primary hyperparathyroidism may occur as part of hereditary syndromes, including multiple endocrine neoplasia types 1 and 2A (MEN1 and MEN2A), hyperparathyroidism-jaw tumor syndrome, and the familial isolated hyperparathyroidism (FIHP). It is unclear whether FIHP corresponds to a different genetic entity or a variant of MEN1 ( or hyperparathyroidism-jaw tumor syndrome). We report a patient and 11 family members with FIHP in whom we identified a heterozygous G-to-A mutation at nucleotide 7361 of tumor suppressor MEN1 gene. This mutation is located in the first base of intron 9 (IVS9 + 1 G>A). All the family members with hyperparathyroidism were heterozygous for the intronic mutation. In vitro studies were performed in COS cells transfected with minigenes carrying the coding regions spanning exon-intron 9 and 10 with the mutant and the wild-type sequences. RT-PCR analyses showed an abnormal mRNA of greater size ( 829 bp) in the mutated MEN1 gene than the normal transcript ( 629 bp). The longer PCR product includes the exon 9, the unspliced intron 9, and part of exon 10. RT-PCR of MEN1 mRNA from patient's blood confirmed the existence of unspliced intron 9 in mature mRNA. In summary, we report a case of FIHP associated with a new intronic heterozygous germline mutation (IVS9 + 1 G> A) of MEN1 gene. This mutation produces an aberrant splicing of mRNA that could lead to a truncated protein, without activity, explaining the clinical picture of this patient and his family.