[AGL gene analysis of a pedigree with glycogen storage disease type III and identification of a novel mutation].
OBJECTIVE
To reveal the molecular genetic pathogenesis of the glycogen storage disease type III (GSDIII) and to provide a prerequisite for prenatal gene diagnosis in future.


METHODS
All the coding regions as well as the border areas between exons and introns of the AGL gene and the parental relevant mutation sites were directly sequenced, so that to affirm the origin of the mutation. Then, detected novel heterozygous mutation was confirmed by cloning sequencing. Finally, definite diagnoses of the novel mutation were performed by a series of identification methods, including screening for the 100 normal controls by DHPLC in order to count the mutational frequency, analyze the conservative of the mutant amino acid sequence from 11 kinds of species and comprise the difference of the tertiary structure between the mutant protein and the normal one.


RESULTS
The patient had compound heterozygous mutations, the c.100C>T (p.R34X) nonsense mutation and c. 1176_1178 del TCA deletion mutation. The p.R34X has been reported abroad, but the 1176_1178 del TCA/p.His392fs mutation is a novel one. The proband's father is heterozygous with the p.R34X mutation while his mother carries the c.1176_1178 del TCA mutation. The result from searching the dbSNP database, HGMD database and papers published in recent years showed that the c.1176_1178 del TCA is a novel mutation, but not an SNP. Conservative analysis results in 11 species indicate that the amino acid of the mutation site is highly conserved in the stage of evolution. Comparison results between the mutant protein and the normal one demonstrate that the deletion mutation results in the obvious variation of the spatial conformation of AGL protein.


CONCLUSIONS
The "c.1176_1178 del TCA (p.392delHis)" mutation is a novel pathogenic mutation. This mutation and the c.100C>T (p.R34X) is the cause that the proband suffer from the GSDIIIa disease. These two mutations are inherited from mother and father respectively. The methods from this paper can be used for further prenatal gene diagnosis.
Department of Medical Genetics, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou 510080, China.
Xiao-yun
XY
Wu
Jing-xin
JX
Pan
Email: guoyibin@mail.sysu.edu.cn.
Yi-bin
YB
Guo
D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D016022:Case-Control Studies; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D006004:Glycogen Debranching Enzyme System / Q000737:chemistry / Q000235:genetics*; D006010:Glycogen Storage Disease Type III / Q000175:diagnosis / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D008297:Male; D009154:Mutation; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D016415:Sequence Alignment
D006004:Glycogen Debranching Enzyme System