Four novel missense mutations in the CYP21A2 gene detected in Russian patients suffering from the classical form of congenital adrenal hyperplasia: identification, functional characterization, and structural analysis.
BACKGROUND
Congenital adrenal hyperplasia is a group of autosomal recessive inherited disorders of steroidogenesis. The most frequent cause is the deficiency of steroid 21-hydroxylase (CYP21) due to mutations in the CYP21A2 gene.


OBJECTIVE
We analyzed the functional and structural consequences of the four CYP21A2 missense mutations (C169R, G178R, W302R, and R426C) to prove their clinical relevance and study their impact on CYP21 function.


RESULTS
Analyzing the mutations in vitro revealed an almost absent or negligible CYP21 activity for the conversion of 17-hydroxyprogesterone to 11-deoxycortisol and progesterone to deoxycorticosterone. Protein translation and intracellular localization were not affected by the mutants, as could be demonstrated by Western blotting and immunofluorescence studies. Analysis of these mutants in a three-dimensional model structure of the CYP21 protein explained the observed in vitro effects because all the mutations severely interfere either directly or indirectly with important structures of the 21-hydroxylase protein.


CONCLUSIONS
The in vitro expression analysis of residual enzyme function is a complementary method to genotyping and an important tool for improving the understanding of the clinical phenotype of 21-hydroxylase deficiency. This forms the foundation for accurate clinical and genetic counseling and for prenatal diagnosis and treatment. Moreover, this report demonstrates that the combination of in vitro enzyme analysis and molecular modeling can yield novel insights into CYP450 structure-functional relationships.
Grischuk
Yulia
Y
Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia.
Rubtsov
Petr
P
Riepe
Felix G
FG
Grötzinger
Joachim
J
Beljelarskaia
Svetlana
S
Prassolov
Vladimir
V
Kalintchenko
Natalya
N
Semitcheva
Tatyana
T
Peterkova
Valentina
V
Tiulpakov
Anatoly
A
Sippell
Wolfgang G
WG
Krone
Nils
N
D000293:Adolescent; D000312:Adrenal Hyperplasia, Congenital / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002648:Child; D002522:Chlorocebus aethiops; D004252:DNA Mutational Analysis; D012734:Disorders of Sex Development / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D011487:Protein Conformation; D011629:Puberty, Precocious / Q000235:genetics; D012426:Russia; D017386:Sequence Homology, Amino Acid; D013255:Steroid 21-Hydroxylase / Q000235:genetics*; D013329:Structure-Activity Relationship
D013255:Steroid 21-Hydroxylase