Novel Mutations in GPR68 and SLC24A4 Cause Hypomaturation Amelogenesis Imperfecta

Amelogenesis imperfecta (AI) is a rare genetic condition affecting the quantity and/or quality of tooth enamel. Hypomaturation AI is characterized by brownish-yellow discoloration with increased opacity and poorly mineralized enamel prone to fracture and attrition. We recruited three families affected by hypomaturation AI and performed whole exome sequencing with selected individuals in each family. Bioinformatic analysis and Sanger sequencing identified and confirmed mutations and segregation in the families. Family 1 had a novel homozygous frameshift mutation in GPR68 gene (NM_003485.3:c.78_83delinsC, p.(Val27Cysfs*146)). Family 2 had a novel homozygous nonsense mutation in SLC24A4 gene (NM_153646.4:c.613C>T, NP_705932.2:p.(Arg205*)). Family 3 also had a homozygous missense mutation in SLC24A4 gene which was reported previously (c.437C>T, p.(Ala146Val)). This report not only expands the mutational spectrum of the AI-causing genes but also improves our understanding of normal and pathologic amelogenesis.

Two Novel ATP2C1 Mutations in Portuguese Patients with Hailey-Hailey Disease

Hailey-Hailey disease (HHD) is a rare autosomal dominant acantholytic dermatosis. It is characterized by a recurrent eruption of vesicles, erosions, and scaly erythematous plaques involving intertriginous areas and first occurring after puberty, mostly in the third or fourth decade. In 2000, mutations in the ATP2C1 gene on band 3q22.1, encoding the secretory pathway Ca2+/Mn2+-ATPase protein 1(hSPCA1), have been identified as the cause of HHD. We report the identification of two novel mutations of ATP2C1 gene in two Portuguese patients, which expands the spectrum of ATP2C1 mutations underlying HHD and provides useful information for genetic counseling.

A Computational Dissection of Spike protein of SARS-CoV-2 Omicron Variant

The emergence of SARS-CoV-2 omicron variant in late November, 2021 and its rapid spread to different countries, warns the health authorities to take initiative to work on containing its spread. The omicron SARS-CoV-2 variant is unusual from the other variants of concerns reported earlier as it harbors many novel mutations in its genome particularly with >30 mutations in the spike glycoprotein alone. The current study investigated the variation in binding mechanism which it carries compared to the wild type. The study also explored the interaction profile of spike-omicron with human ACE2 receptor. The structure of omicron spike glycoprotein was determined though homology modeling. The interaction analysis was performed through docking using HADDOCK followed by binding affinity calculation. Finally, the comparison of interactions were performed among spike-ACE2 complex of wild type, delta and omicron variants. The interaction analysis has revealed the involvement of highly charged and polar residues (H505, Arg498, Ser446, Arg493, and Tyr501) in the interactions. The important novel interactions in the spike-ACE2-omicron complex was observed as S494:H34, S496:D38, R498:Y41, Y501:K353, and H505:R393 and R493:D38. Moreover, the binding affinity of spike-ACE2-omicron complex (-17.6Kcal/mol) is much higher than wild type-ACE2 (-13.2Kcal/mol) and delta-ACE2 complex (-13.3Kcal/mol). These results indicate that the involvement of polar and charged residues in the interactions with ACE2 may have an impact on increased transmissibility of omicron variant.

Novel mutations in PDE6A and CDHR1 cause retinitis pigmentosa in Pakistani families

AIM: To investigate the genetic basis of autosomal recessive retinitis pigmentosa (arRP) in two consanguineous/ endogamous Pakistani families. METHODS: Whole exome sequencing (WES) was performed on genomic DNA samples of patients with arRP to identify disease causing mutations. Sanger sequencing was performed to confirm familial segregation of identified mutations, and potential pathogenicity was determined by predictions of the mutations’ functions. RESULTS: A novel homozygous frameshift mutation [NM_000440.2:c.1054delG, p. (Gln352Argfs*4); Chr5:g.149286886del (GRCh37)] in the PDE6A gene in an endogamous family and a novel homozygous splice site mutation [NM_033100.3:c.1168-1G>A, Chr10:g.85968484G>A (GRCh37)] in the CDHR1 gene in a consanguineous family were identified. The PDE6A variant p. (Gln352Argfs*4) was predicted to be deleterious or pathogenic, whilst the CDHR1 variant c.1168-1G>A was predicted to result in potential alteration of splicing. CONCLUSION: This study expands the spectrum of genetic variants for arRP in Pakistani families.

Three novel mutations of the BCKDHA, BCKDHB and DBT genes in Chinese children with maple syrup urine disease

Background Maple syrup urine disease (MSUD) is a rare metabolic autosomal recessive disorder caused by deficiency of the branched-chain α-ketoacid dehydrogenase complex. Mutations in the BCKDHA, BCKDHB and DBT genes are responsible for MSUD. This study presents the clinical and molecular characterizations of four MSUD patients. Methods Clinical data of patients were retrospectively analyzed, and genetic mutations were identified by whole-exome sequencing. CLUSTALX was employed to analyzed cross-species conservation of the mutant amino acid. The impact of the mutations was analyzed with PolyPhen-2 software. The I-TASSER website and PyMOL software were used to predict the protein three-position structure of the novel mutations carried by the patients. Results Vomiting, irritability, feeding difficulties, seizures, dyspnoea, lethargy and coma were the main clinical presentations of MSUD. Cranial MRI showed abnormal symmetrical signals in accordance with the presentation of inherited metabolic encephalopathy. Seven mutations were detected in four patients, including three novel pathogenic mutations in the BCKDHA (c.656C>A), BCKDHB (deletion of a single-copy of BCKDHB) and DBT (c.1219dup) genes. Structural changes were compatible with the observed phenotypes. Conclusions Different types of MSUD can display heterogeneous clinical manifestations. Exhaustive molecular studies are necessary for a proper differential diagnosis. The newly identified mutation will play a key role in the prenatal diagnosis of MSUD in the future.

Two Novel Mutations in the SI Gene Associated With Congenital Sucrase-Isomaltase Deficiency: A Case Report in China

Background: Congenital sucrase-isomaltase deficiency (CSID) is an autosomal recessive inherited disease that leads to the maldigestion of disaccharides and is associated with mutation of the sucrase-isomaltase (SI) gene. Cases of CSID are not very prevalent in China or worldwide but are gradually being identified and reported.Case Presentation: We report a case involving a 14-month-old male who presented with failure to thrive that had begun after food diversification and was admitted for chronic diarrhea. We used a whole-exome sequencing (WES) approach to identify mutations in this patient's genome. WES revealed two novel heterozygous mutations in the SI gene, c.2626C > T (p.Q876*) and c.2872C > T (p.R958C), which were confirmed by Sanger DNA sequencing. With a strict sucrose- and starch-restricted diet, the patient's diarrhea was resolved, and he began to gain weight.Conclusions: We report a case of novel variants in the SI gene that caused CSID. This report provides valuable information for the clinical field, especially in China.

Frequent SLC12A3 mutations in Chinese Gitelman syndrome patients: structure and function disorder

Purposes: This study was conducted to identify the frequent mutations from reported Chinese Gitelman syndrome (GS) patients, to predict three-dimensional structure change of human Na-Cl co-transporter (hNCC), and to test the activity of these mutations and some novel mutations in vitro and in vivo. Methods: SLC12A3 gene mutations in Chinese GS patients previously reported in the PubMed, CNKI and Wanfang database were summarized. Predicted configurations of wild type (WT) and mutant proteins were achieved using the I-TASSER workplace. Six missense mutations (T60M, L215F, D486N, N534K, Q617R and R928C) were generated by site-directed mutagenesis. 22Na+ uptake experiment was carried out in the Xenopus laevis oocyte expression system. 35 GS patients and 20 healthy volunteers underwent the thiazide test. Results: T60M, T163M，D486N, R913Q, R928C and R959 frameshift were frequent SLC12A3 gene mutations (mutated frequency >3%) in 310 Chinese GS families. The protein’s three-dimensional structure was predicted to be altered in all mutations. Compared with WT hNCC, the thiazide-sensitive 22Na+ uptake was significantly diminished for all 6 mutations: T60M 22±9.2%, R928C 29±12%, L215F 38±14%, N534K 41±15.5%, Q617R 63±22.1% and D486N 77±20.4%. In thiazide test, the net increase in chloride fractional excretion in 20 healthy controls was significantly higher than GS patients with or without T60M or D486N mutations. Conclusions: Frequent mutations (T60M, D486N, R928C) and novel mutations (L215F, N534K and Q617R) lead to protein structure alternation and protein dysfunction verified by 22Na+ uptake experiment in vitro and thiazide test on patients.