Identification and functional analysis of GCK gene mutations in 12 Chinese families with hyperglycemia.
AIMS/INTRODUCTION
To investigate the clinical and genetic characteristics of Chinese patients with a phenotype consistent with maturity-onset diabetes of the young type 2 and explore the pathogenic mechanism of their hyperglycemia.


MATERIALS AND METHODS
We studied 12 probands and their extended families referred to our center for screening mutations in the glucokinase gene (GCK). Clinical data were collected and genetic analysis was carried out. The recombinant wild-type and mutant glucokinase were generated in Escherichia coli. The kinetic parameters and thermal stability of the enzymes were determined in vitro.


RESULTS
In the 12 families, 11 GCK mutations (R43C, T168A, K169N, R191W, Y215X, E221K, M235T, R250H, W257X, G261R and A379E) and one variant of uncertain significance (R275H) were identified. R191W was detected in two unrelated families. Of the 11 GCK mutations, three mutations (c.507G>C, K169N; c.645C>A, Y215X; c.771G>A, W257X; NM_000162.3, NP_000153.1) are novel. Basic kinetics analysis explained the pathogenicity of the five mutants (R43C, K169N, R191W, E221K and A379E), which showed reduced enzyme activity with relative activity indexes between ~0.001 and 0.5 compared with the wild-type (1.0). In addition, the thermal stabilities of these five mutants were also decreased to varying degrees. However, for R250H and R275H, there was no significant difference in the enzyme activity and thermal stability between the mutants and the wild type.


CONCLUSIONS
We have identified 11 GCK mutations and one variant of uncertain significance in 12 Chinese families with hyperglycemia. For five GCK mutations (R43C, K169N, R191W, E221K and A379E), the changes in enzyme kinetics and thermostability might be the pathogenic mechanisms by which mutations cause hyperglycemia.
['Wang|Zhixin|Z|', 'Diao|Chengming|C|', 'Liu|Yijing|Y|', 'Li|Mingmin|M|', 'Zheng|Jia|J|', 'Zhang|Qian|Q|', 'Yu|Miao|M|', 'Zhang|Huabing|H|', 'Ping|Fan|F|http://orcid.org/0000-0001-7650-6612', 'Li|Ming|M|', 'Xiao|Xinhua|X|']
D000293:Adolescent D000328:Adult D044466:Asians D015415:Biomarkers D002648:Child D002675:Child, Preschool D005260:Female D005500:Follow-Up Studies D005820:Genetic Testing D000081410:Germinal Center Kinases D006801:Humans D006943:Hyperglycemia D007231:Infant, Newborn D008297:Male D009154:Mutation D010375:Pedigree D010641:Phenotype D011379:Prognosis D055815:Young Adult
Maturity-onset diabetes of the young Glucokinase Enzyme kinetics