[Phenotypic and genotypic analysis of a fetus carrying an intermediate 22q11.2 deletion encompassing the CRKL gene].

OBJECTIVE

To delineate the phenotypic characteristics of 22q11.2 deletion syndrome and the role of CRKL gene in the pathogenesis of cardiac abnormalities.

METHODS

G-banded karyotyping, single nucleotide polymorphism (SNP) array and fluorescence in situ hybridization (FISH) were performed on a fetus with tetralogy of Fallot detected by ultrasound. Correlation between the genotype and phenotype was explored after precise mapping of the breakpoints on chromosome 22q11.2. SNP array was also performed on peripheral blood samples from both parents to clarify its origin.

RESULTS

The fetus showed a normal karyotype of 46,XY. SNP array performed on fetal blood sample revealed a 749 kb deletion (chr22: 20 716 876-21 465 659) at 22q11.21, which encompassed the CRKL gene but not TBX1, HIRA, COMT and MAPK1. Precise mapping of the breakpoints suggested that the deleted region has overlapped with that of central 22q11.2 deletion syndrome. SNP array analysis of the parental blood samples suggested that the 22q11.21 deletion has a de novo origin. The presence of 22q11.21 deletion in the fetus was also confirmed by FISH analysis.

CONCLUSION

Central 22q11.21 deletion probably accounts for the cardiac abnormalities in the fetus, for which the CRKL gene should be considered as an important candidate.