The Application of Next-Generation Sequencing (NGS) in Neonatal-Onset Urea Cycle Disorders (UCDs): Clinical Course, Metabolomic Profiling, and Genetic Findings in Nine Chinese Hyperammonemia Patients

Abstract

During Jan. 2016–Dec. 2019, nine Chinese patients from eight unrelated families were diagnosed with neonatal-onset UCDs by targeted panel sequencing or whole-exome sequencing (WES). Their clinical manifestations, biochemical features, 180-day-age outcomes, and molecular genetic characteristics were reviewed retrospectively. NGS-based tests revealed 7 patients diagnosed with ornithine transcarbamylase deficiency (OTCD) and 2 with carbamoylphosphate synthetase I deficiency (CPS1D). The spectrum of the clinical presentation of nine affected individuals progressed from unspecific symptoms like poor feeding to somnolence, coma, and death. All patients presented with an acute hyperammonemia. The most robust metabolic pattern in OTCD was hyperglutaminemic hyperammonemia with high concentration of urine orotic acid, and it was reported in six patients. Of ten variants found on the OTC gene and CPS1 gene, 3 were novel: (c.176T>C (p.L59P)) in the OTC gene, c.2938G>A (p.G980S) and c.3734T>A (p.L1245H) in the CPS1 gene. There was a high mortality rate of 77.78% (7/9) for all the defects combined. An OTC-deficient male and a CPS1-deficient female survived from episodes of hyperammonemia. Although prompt recognition of UCD and the use of alternative pathway therapy in addition to provision of appropriate nutrition and dialysis improved survival, the overall outcomes for the neonatal-onset type are poor in China.

New and sex-specific migraine susceptibility loci identified from a multiethnic genome-wide meta-analysis

“…Mutations in this gene have been associated with metabolic deficiencies such as urea cycle disorder and hyperammonemia 53,54 . Individuals with a CPS1 deficiency can present with a wide range of clinical manifestations, including headache, behavioral or psychiatric problems, learning disabilities, sleep disorder, periodic vomiting, seizures, coma, and even death [55][56][57] . SLC25A21 (also known as ODC1) encodes the solute carrier family 25 member 21, which is essential for ammonium fixation and lysine biosynthesis 58 .…”

Common polymorphic OTC variants can act as genetic modifiers of enzymatic activity

“…Although significantly reduced by comparison with wild-type, the level of enzymatic activity associated with the various versions of OTC harboring the p.Arg40His mutation may well be enough to F I G U R E 4 Structural analysis of Site 2 in OTC homology models. OTC, ornithine transcarbamylase sustain quasi-normal metabolic status as several OTC deficiency patients have been reported in the literature as presenting symptoms at distinct ages (Cavicchi et al, 2014;Hidaka et al, 2020;Koya et al, 2019;Matsuda et al, 1996;Pinner et al, 2010;Ploechl et al, 2001;Tuchman et al, 1994;Yoshino et al, 1990;Zhou et al, 2020). The interplay between rare disease-causing mutations and common polymorphic variants has been documented for only a very limited number of genes/proteins involved in human genetic disease (Chan et al, 2006;Cheng et al, 2011;Cooper et al, 2010;Gonzalez & Ostermeier, 2019;Lage et al, 2014;Li et al, 2018;Matsumura et al, 2017;Niu et al, 2006;Poelzing et al, 2006;Raef et al, 2008;Silva et al, 2004;Zhang et al, 2008).…”

“…The majority of these lesions are private or found in very few families (Yamaguchi et al, 2006 ). One exception is the p.Arg40His replacement (NM_000531.5:c.119G>A [p.Arg40His]) which has been reported in a number of distinct families as a consequence of both recurrent and identical‐by‐descent mutation (Hidaka et al, 2020 ; Koya et al, 2019 ; Matsuda et al, 1996 ; Nishiyori et al, 1997 ; Zhou, Huang, Ma & Zhu, 2020 ). OTC activity measured from the necropsied liver of five deceased patients with a confirmed p.Arg40His mutation has been found to be between 1.3% and 12% of the wild‐type OTC level (Matsuda et al, 1996 ) whereas the mutant (p.Arg40His‐harboring) OTC enzyme expressed in vitro in COS‐1 cells exhibited 10.2% (Matsuda et al, 1996 ) to 28% (Nishiyori et al, 1997 ) of wild‐type activity.…”

Application of Next Generation Sequencing Genetic Studies of Urea Cycle Disorders

“…Bệnh thiếu hụt CPS1, gây ra do các đột biến trên gen CPS1, là một rối loạn di truyền lặn trên nhiễm sắc thể thường. Đây là một trong những bệnh thuộc nhóm UCD nghiêm trọng nhất với tỷ lệ mắc ước tính là 1/1.300.000 [15]. Hiện nay, cơ sở dữ liệu ClinVar đã cập nhật 491 đột biến gây bệnh trên gen CPS1.…”

“…Các kết quả lâm sàng, sinh hóa và sàng lọc di truyền là cơ sở để xác nhận 3 bệnh nhân mắc bệnh thiếu hụt OTC [24]. Trong số 10 đột biến được tìm thấy trên gen OTC và CPS1 ở 9 bệnh nhân Trung Quốc chẩn đoán UCD khởi phát sơ sinh bằng giải trình tự toàn bộ vùng exon có 1 đột biến mới (c.176T>C, p.L59P), và 6 đột biến đã được ghi nhận (c.119G>A, p.R40H; c.540G>C, p.Q180H; c.803T>C, p.M268T; c.626C>T, p.A209V; c.626C>T, p.A209V) trên gen OTC [15]. Nghiên cứu của Olga và cộng sự (2021) sử dụng phương pháp WES đã phát hiện được 1 đột biến dịch khung mới, c.78-1G˃A, trên exon 2, gen OTC làm mất 1bp và dịch chuyển khung đọc c.78delG (p.C27Vfs*11) ở bé gái, 4 tuổi với các triệu chứng như, từ chối ăn thịt, rối loạn thần kinh, chậm nói, nồng độ ala-ninefminotransferase (ALT), aspartate aminotransferase (AST) tăng gấp 10 lần.…”