Kuptanon Chulaluk, Morimoto Marie, Nicoli Elena-Raluca, Stephen Joshi, Yarnell David S, Dorward Heidi, Owen William, Parikh Suhag, Ozbek Namik Yasar, Malbora Baris, Ciccone Carla, Gunay-Aygun Meral, Gahl William A, Introne Wendy J, Malicdan May Christine V
Human Biochemical Genetics Section, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, United States.
National Institutes of Health Undiagnosed Diseases Program, National Institutes of Health Common Fund, Office of the Director, National Institutes of Health, Bethesda, MD, United States.
Front Genet. 2023 Mar 8;14:1072784. doi: 10.3389/fgene.2023.1072784. eCollection 2023.
Chediak-Higashi syndrome (CHS) is rare autosomal recessive disorder caused by bi-allelic variants in the Lysosomal Trafficking Regulator () gene. Diagnosis is established by the detection of pathogenic variants in in combination with clinical evidence of disease. Conventional molecular genetic testing of by genomic DNA (gDNA) Sanger sequencing detects the majority of pathogenic variants, but some remain undetected for several individuals clinically diagnosed with CHS. In this study, cDNA Sanger sequencing was pursued as a complementary method to identify variant alleles that are undetected by gDNA Sanger sequencing and to increase molecular diagnostic yield. Six unrelated individuals with CHS were clinically evaluated and included in this study. gDNA Sanger sequencing and cDNA Sanger sequencing were performed to identify pathogenic variants. Ten novel alleles were identified, including eight nonsense or frameshift variants and two in-frame deletions. Six of these were identified by conventional gDNA Sanger sequencing; cDNA Sanger sequencing was required to identify the remaining variant alleles. By utilizing cDNA sequencing as a complementary technique to identify variants, a complete molecular diagnosis was obtained for all six CHS patients. In this small CHS cohort, the molecular diagnostic yield was increased, and canonical splice site variants identified from gDNA Sanger sequencing were validated by cDNA sequencing. The identification of novel alleles will aid in diagnosing patients and these molecular diagnoses will also lead to genetic counseling, access to services and treatments and clinical trials in the future.
切迪阿克-东综合征（CHS）是一种罕见的常染色体隐性疾病，由溶酶体运输调节因子（LYST）基因的双等位基因变异引起。通过检测LYST基因中的致病变异并结合疾病的临床证据来确诊。通过基因组DNA（gDNA）桑格测序对LYST进行常规分子遗传学检测可检测到大多数致病变异，但仍有一些临床诊断为CHS的个体未被检测到。在本研究中，采用cDNA桑格测序作为一种补充方法，以鉴定gDNA桑格测序未检测到的变异等位基因，并提高分子诊断率。对6名无关的CHS个体进行了临床评估并纳入本研究。进行gDNA桑格测序和cDNA桑格测序以鉴定致病的LYST变异。共鉴定出10个新的LYST等位基因，包括8个无义或移码变异和2个框内缺失。其中6个是通过常规gDNA桑格测序鉴定的；其余变异等位基因需要通过cDNA桑格测序来鉴定。通过利用cDNA测序作为鉴定LYST变异的补充技术，6名CHS患者均获得了完整的分子诊断。在这个小的CHS队列中，分子诊断率提高了，并且通过cDNA测序验证了从gDNA桑格测序中鉴定出的典型剪接位点变异。新LYST等位基因的鉴定将有助于诊断患者，这些分子诊断也将在未来带来遗传咨询、获得服务和治疗以及开展临床试验。
