Thesis (Ph.D.)--Chulalongkorn University, 2015

Whole exome sequencing (WES) is an application of the next generation sequencing (NGS). With this technique, the target regions such as coding sequences, splice site, non-coding RNA and highly conserved regions which are about 1 percent of the genome harboring about 85 percent of mutations with large effects on disease-related traits are sequenced. Here, two different Mendelian disorders were studied. The first is familial comedones, a rare autosomal dominant skin disorder. Two unrelated families affected with familial comedones were included. WES combined with whole genome linkage analysis using a single nucleotide polymorphism (SNP) array was conducted in the first family which identified a heterozygous mutation, c.84_85insT in the PSENEN gene. This mutation was also identified in the second family. Quantitative real-time PCR indicated increased expression of PSENEN mRNA in the patients. Another disease included in this study is an undiagnosed syndrome with intellectual disability in a non-consanguineous family. Two siblings were affected. Exome sequencing was performed in both patients and their parents. Neither pathogenic copy number variations nor SNVs/indels were identified. In summary, conducting WES led us to identify a novel gene underlying familial comedones. However, using WES to find a gene underlying a disease with genetic heterogeneity as intellectual disability remains a challenge.