Objective: To analyze chromosome aberration in a child with mental retardation and abnormalities and its parents.
Methods: Chromosome G banding, multiplex ligation-dependent probe amplification, fluorescence in situ hybridization and single nucleotide polymorphisms array were employed for analysis.
Results: Karyotype analysis revealed that the child was 46,XX and the father was 46,XY, while the mother was 46,XX, add (12)(p13). Subtelomeric region analysis with MLPA displayed that the child has reduced ACP1 gene copy number in 2p25 region and increased SLC6A12,KDM5A gene copy numbers in 12p11 region. SNP-array has fine mapped the duplication to 12p13.33-p12.3, a 15.142 Mb region, and a deletion to 2p25.3 for 3.194 Mb, which resulted in duplication of 9 genes including SLC6A12 as well as deletion of 11 genes including SNTG2, respectively. FISH analysis revealed that the child was 46,XX,ish,der(2),t(2;12)(p25;p13)mat, or partial monosomy 2p25 and partial trisomy 12p13. In addition,the mother was a carrier with cryptic balanced translocation chromosome, 46,XX,isht(2;12) (p25;p13). Mental abnormalities and retardation of the child may be attributed to heterozygous deletion of SNTG2, MYT1L genes and duplication of SLC6A12 gene.
Conclusion: Combined use of MLPA, FISH and SNP-array can facilitate accurate diagnosis of cryptic rearrangement at genomic level.