A family of autosomal dominant hypocalcemia with an activating mutation of calcium-sensing receptor gene.

Autosomal dominant hypocalcemia (ADH) caused by activating mutations of calcium-sensing receptor (CaSR) is characterized by hypocalcemia with inappropriately low concentration of PTH and relative hypercalciuria. Active vitamin D treatment often leads to nephrolithiasis and renal impairment in patients with ADH. However, differential diagnosis between ADH and idiopathic hypoparathyroidism is sometimes very difficult. Here, we report a mutation of CaSR and its functional property found in three generations of a Japanese family. The proband developed seizures at 7 days of age. His mother and elder sister were discovered to have hypoparathyroidism by family survey, but his father was normocalcemic. His grandfather developed heart failure and was found to have hypoparathyroidism. All affected members had been treated with active vitamin D3 and bilateral nephrolithiasis were detected in three of them. DNA sequencing revealed that all affected patients had a heterozygous mutation in CaSR gene that causes proline to leucine substitution at codon 221 (P221L). In vitro functional analysis of the mutant CaSR by measuring inositol 1,4,5-trisphosphate production in response to changes of extracellular Ca indicated that this mutation is an activating one and responsible for ADH in this family. Therefore, careful monitoring of urinary Ca excretion before and during treatment of PTH-deficient hypoparathyroidism is very important, and screening of CaSR mutation should be considered in patients with relative hypercalciuria or with a family history of hypocalcemia.

A minigene containing four discrete cis elements recapitulates GATA-1 gene expression in vivo.

BACKGROUND: The GATA-1haematopoietic enhancer (G1HE), located between 3.9 and 2.6 kb 5' to the haematopoietic first exon, is essential for GATA-1 gene transcription in erythroid cells. However, G1HE is not sufficient to confer tissue specificity on the GATA-1 gene in vivo, indicating that additional regulatory sequences are necessary. RESULTS: We demonstrate here that two other upstream promoter elements containing a double GATA motif or two CACCC boxes are also indispensable for reporter gene expression in erythroid cells in the transgenic mouse. The combination of these three cis-acting regions was sufficient for reporter expression in primitive erythroid cells, as demonstrated by linking the elements together into a 659 bp artificial (GdC) minigene. The minigene activated the transcription of a reporter gene from either the endogenous or an exogenous thymidine kinase promoter, retaining cell type-specificity. The addition of a 320 bp fragment in the first intron to the GdC minigene sustained reporter expression in the definitive stage. Moreover, a line of transgenic mouse that expressed GATA-1 cDNA under the control of the complete 979 bp minigene rescued GATA-1 germ line mutant mice from embryonic lethality. CONCLUSIONS: A combination of four distinct sequence motifs co-operatively serve as a fundamental functional unit for GATA-1 erythroid transcription in vivo.