Characterization of a novel Alu-Alu recombination-mediated genomic deletion in the TCIRG1 gene in five osteopetrotic patients.
Human malignant autosomal recessive osteopetrosis (ARO) is a genetically heterogeneous disorder caused by reduced bone resorption by osteoclasts. Biallelic mutations in the TCIRG1 gene, encoding the a3 subunit of the vacuolar proton pump, are responsible for more than one half of ARO patients. However, a few patients with monoallelic mutations have been described, raising the possibility of a dominant-like TCIRG1-dependent osteopetrosis, of a digenic disease, or of peculiar mutations difficult to detect with standard methods. We describe here a novel genomic deletion in the TCIRG1 gene explaining why, in some patients, mutations in only one allele have previously been found. The analysis of a proband from a consanguineous Turkish family allowed us to define the deletion boundaries encompassing introns 10 and 13 and occurring within AluSx repeat sequences, suggesting Alu-mediated homologous recombination as a mechanism. An identical genomic deletion at the heterozygous level was found in four unrelated Italian families in whom only a single mutated allele has previously been found. TCIRG1 haplotype analysis in these five families suggests a possible common ancestral origin for this large deletion. In summary, we describe the identification of a novel genomic deletion in the TCIRG1 gene that is of clinical relevance, especially in prenatal diagnosis.
Pangrazio
Alessandra
A
Institute for Biomedical Technologies, National Research Council, Segrate, Italy.
Caldana
Maria Elena
ME
Sobacchi
Cristina
C
Panaroni
Cristina
C
Susani
Lucia
L
Mihci
Ercan
E
Cavaliere
Maria Luigia
ML
Giliani
Silvia
S
Villa
Anna
A
Frattini
Annalisa
A
D020087:Alu Elements; D001483:Base Sequence; D003241:Consanguinity; D005192:Family Health; D017353:Gene Deletion; D005808:Genes, Recessive; D006579:Heterozygote; D006801:Humans; D007558:Italy; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010022:Osteopetrosis / Q000235:genetics*; D011995:Recombination, Genetic; D014421:Turkey; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics*
C472421:TCIRG1 protein, human; D025262:Vacuolar Proton-Translocating ATPases