Complete sequencing of expanded SAMD12 repeats by long-read sequencing and Cas9-mediated enrichment

A pentanucleotide TTTCA repeat insertion into a polymorphic TTTTA repeat element in SAMD12 causes benign adult familial myoclonic epilepsy. Although the precise determination of the entire SAMD12 repeat sequence is important for molecular diagnosis and research, obtaining this sequence remains challenging when using conventional genomic/genetic methods, and even short-read and long-read next-generation sequencing technologies have been insufficient.

Incomplete information regarding expanded repeat sequences may hamper our understanding of the pathogenic roles played by varying numbers of repeat units, genotype-phenotype correlations, and mutational mechanisms. Here, we report a new approach for the precise determination of the entire expanded repeat sequence and present a workflow designed to improve the diagnostic rates in various repeat expansion diseases.

Authors: Takeshi Mizuguchi, Tomoko Toyota, Satoko Miyatake, Satomi Mitsuhashi, Hiroshi Doi, Yosuke Kudo, Hitaru Kishida, Noriko Hayashi, Rie S Tsuburaya, Masako Kinoshita, Tetsuhiro Fukuyama, Hiromi Fukuda, Eriko Koshimizu, Naomi Tsuchida, Yuri Uchiyama, Atsushi Fujita, Atsushi Takata, Noriko Miyake, Mitsuhiro Kato, Fumiaki Tanaka, Hiroaki Adachi, Naomichi Matsumoto