Use of clinical chromosomal microarray in Chinese patients with autism spectrum disorder—implications of a copy number variation involving DPP10

Annisa Shui Lam Mak, Annie Ting Gee Chiu, Gordon Ka Chun Leung, Christopher Chun Yu Mak, Yoyo Wing Yiu Chu, Gary Tsz Kin Mok, Wing Fai Tang, Kelvin Yuen Kwong Chan, Mary Hoi Yin Tang, Elizabeth Tak-Kwong Lau Yim, Kin Wai So, Victoria Qinchen Tao, Cheuk Wing Fung, Virginia Chun Nei Wong, Mohammed Uddin, So Lun Lee, Christian R. Marshall, Stephen W. Scherer, Anita Sik Yau Kan, Brian Hon Yin Chung

Array comparative genomic hybridization (aCGH) is recommended as a first-tier genetic test for children with autism spectrum disorder (ASD). However, interpretation of results can often be challenging partly due to the fact that copy number variants (CNVs) in non-European ASD patients are not well studied. To address this literature gap, we report the CNV findings in a cohort of Chinese children with ASD. DNA samples were obtained from 258 Chinese ASD patients recruited from a child assessment center between January 2011 and August 2014. aCGH was performed using NimbleGen-CGX-135k or Agilent-CGX 60k oligonucleotide array. Results were classified based on existing guidelines and literature. Ten pathogenic CNVs and one likely pathogenic CNV were found in nine patients, with an overall diagnostic yield of 3.5%. A 138 kb duplication involving 3' exons of DPP10 (arr[GRCh37] 2q14.1(116534689_116672358)x3), reported to be associated with ASD, was identified in one patient (0.39%). The same CNV was reported as variant of uncertain significance (VUS) in DECIPHER database. Multiple individuals of typical development carrying a similar duplication were identified among our ancestry-matched control with a frequency of 6/653 (0.92%) as well as from literature and genomic databases. The DPP10 duplication is likely a benign CNV polymorphism enriched in Southern Chinese with a population frequency of ~1%. This highlights the importance of using ancestry-matched controls in interpretation of aCGH findings.