Gene mutation analyses in Chinese children with multiple carboxylase deficiency

Objective To confirm the diagnosis of multiple carboxylase deficiency (MCD) on the gene level and explore the mutations in Chinese children with MCD. Methods Biotinidase (BT) and holocarboxylase synthetase (HLCS) genes were analyzed by PCR and direct sequencing for the 4 BT deficiency patients and 8 HLCS deficiency patients, respectively. The identified mutations in the parents of the patients and 50 normal controls were screened by PCR-restriction fragment length polymorphism and direct DNA sequencing. Results Total detection rate of gene mutation is 100% in the 12 children with MCD. Six mutations were detected in the 4 children with BT deficiency, they were c. 98-104del7ins3, c.1369G>A (V457M), c. 1157G>A(W386X), c. 1284C>A(Y428X), c.1384delA and c.1493_1494insT,The last four were novel mutations. Four mutations were found in the 8 children with HLCS deficiency.They were c. 126G>T(E42D),c.1994G>C(R665P), c.1088T>A (V363D and c. 1522C>T (R508W).The last two were hot-spot mutations [75%(12/16)], and c. 1994G>C(R665P)was a novel mutation.Conclusion This study confirmed the diagnosis of 12 patients with MCD on the gene level. Six mutations were found in the BT gene and 4 in the HLCS gene, including 5 novel mutations. Two mutations of the HLCS gene are probably hot-spot mutations in Chinese children with HLCS deficiency. Key words: biotinidase;  holocarboxylase;  tandem mass spectrometry;  mutation;  multiple carboxylase deficiency