Pentanucleotide Repeat Insertions in RAI1 Cause Benign Adult Familial Myoclonic Epilepsy Type 8.

BACKGROUND: Benign adult familial myoclonic epilepsy (BAFME) is an autosomal dominant disorder characterized by cortical tremors and seizures. Six types of BAFME, all caused by pentanucleotide repeat expansions in different genes, have been reported. However, several other BAFME cases remain with no molecular diagnosis. OBJECTIVES: We aim to characterize clinical features and identify the mutation causing BAFME in a large Malian family with 10 affected members. METHODS: Long-read whole genome sequencing, repeat-primed polymerase chain reaction and RNA studies were performed. RESULTS: We identified TTTTA repeat expansions and TTTCA repeat insertions in intron 4 of the RAI1 gene that co-segregated with disease status in this family. TTTCA repeats were absent in 200 Malian controls. In the affected individuals, we found a read with only nine TTTCA repeat units and somatic instability. The RAI1 repeat expansions cause the only BAFME type in which the disease-causing repeats are in a gene associated with a monogenic disorder in the haploinsufficiency state (ie, Smith-Magenis syndrome [SMS]). Nevertheless, none of the Malian patients exhibited symptoms related to SMS. Moreover, leukocyte RNA levels of RAI1 in six Malian BAFME patients were no different from controls. CONCLUSIONS: These findings establish a new type of BAFME, BAFME8, in an African family and suggest that haploinsufficiency is unlikely to be the main pathomechanism of BAFME. © 2023 International Parkinson and Movement Disorder Society. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Rapid exome sequencing as the first-tier investigation for diagnosis of acutely and severely ill children and adults in Thailand.

The use of rapid DNA sequencing technology in severely ill children in developed countries can accurately identify diagnoses and positively impact patient outcomes. This study sought to evaluate the outcome of Thai children and adults with unknown etiologies of critical illnesses with the deployment of rapid whole exome sequencing (rWES) in Thailand. We recruited 54 unrelated patients from 11 hospitals throughout Thailand. The median age was 3 months (range, 2 days-55 years) including 47 children and 7 adults with 52% males. The median time from obtaining blood samples to issuing the rWES report was 12 days (range, 5-27 days). A molecular diagnosis was established in 25 patients (46%), resulting in a change in clinical management for 24 patients (44%) resulting in improved clinical outcomes in 16 patients (30%). Four out of seven adult patients (57%) received the molecular diagnosis which led to a change in management. The 25 diagnoses comprised 23 different diseases. Of the 34 identified variants, 15 had never been previously reported. This study suggests that use of rWES as a first-tier investigation tool can provide tremendous benefits in critically ill patients with unknown etiology across age groups in Thailand.

The Thai reference exome (T-REx) variant database.

To maximize the potential of genomics in medicine, it is essential to establish databases of genomic variants for ethno-geographic groups that can be used for filtering and prioritizing candidate pathogenic variants. Populations with non-European ancestry are poorly represented among current genomic variant databases. Here, we report the first high-density survey of genomic variants for the Thai population, the Thai Reference Exome (T-REx) variant database. T-REx comprises exome sequencing data of 1092 unrelated Thai individuals. The targeted exome regions common among four capture platforms cover 30.04 Mbp on autosomes and chromosome X. 345 681 short variants (18.27% of which are novel) and 34 907 copy number variations were found. Principal component analysis on 38 469 single nucleotide variants present worldwide showed that the Thai population is most genetically similar to East and Southeast Asian populations. Moreover, unsupervised clustering revealed six Thai subpopulations consistent with the evidence of gene flow from neighboring populations. The prevalence of common pathogenic variants in T-REx was investigated in detail, which revealed subpopulation-specific patterns, in particular variants associated with erythrocyte disorders such as the HbE variant in HBB and the Viangchan variant in G6PD. T-REx serves as a pivotal addition to the current databases for genomic medicine.

Four novel mutations of FAM20A in amelogenesis imperfecta type IG and review of literature for its genotype and phenotype spectra.

Amelogenesis imperfecta type IG (AI1G) is caused by mutations in FAM20A. Genotypic and phenotypic features of AI1G are diverse and their full spectra remain to be characterized. The aim of this study was to identify and summarize variants in FAM20A in a broad population of patients with AI1G. We identified a Thai female (Pt-1) and a Saudi male (Pt-2) affected with AI1G. Both had hypoplastic enamel, gingival hyperplasia, and intrapulpal calcification. Pt-1 also had rapidly progressive embedding of unerupted teeth, early eruption of permanent teeth, and spontaneous dental infection. Uniquely, Pt-2 had all permanent teeth erupted which was uncommon in AI1G patients. Whole exome sequencing (WES) identified that Pt-1 was heterozygous for FAM20A, c.758A > G (p.Tyr253Cys), inherited from her father. The mutation on maternal allele was not detected by WES. Pt-2 possessed compound heterozygous mutations, c.1248dupG (p.Phe417Valfs*7); c.1081C > T (p.Arg361Cys) in FAM20A. Array comparative genomic hybridization (aCGH), cDNA sequencing, and whole genome sequencing successfully identified 7531 bp deletion on Pt-1's maternal allele. This was the largest FAM20A deletion ever found. A review of all 70 patients from 50 independent families with AI1G (including two families in this study) showed that the penetrance of hypoplastic enamel and gingival hyperplasia was complete. Unerupted permanent teeth were found in all 70 patients except Pt-2. Exons 1 and 11 were mutation-prone. Most mutations were frameshift. Certain variants showed founder effect. To conclude, this study reviews and expands phenotypic and genotypic spectra of AI1G. A large deletion missed by WES can be detected by WGS. Hypoplastic enamel, gingival hyperplasia, and unerupted permanent teeth prompt genetic testing of FAM20A. Screening of nephrocalcinosis, early removal of embedded teeth, and monitoring of dental infection are recommended.

TTTCA repeat insertions in an intron of YEATS2 in benign adult familial myoclonic epilepsy type 4.

Epilepsy is a common neurological disorder and identification of its causes is important for a better understanding of its pathogenesis. We previously studied a Thai family with a type of epilepsy, benign adult familial myoclonic epilepsy type 4 (BAFME4), and localized its gene to chromosome 3q26.32-q28. Here, we used single-molecule real-time sequencing and found expansions of TTTTA and insertions of TTTCA repeats in intron 1 of YEATS2 in one affected member of the family. Of all the available members in the family-comprising 13 affected and eight unaffected-repeat-primed PCR and long-range PCR revealed the co-segregation of the TTTCA repeat insertions with the TTTTA repeat expansions and the disease status. For 1116 Thai control subjects, none were found to harbour the TTTCA repeats while four had the TTTTA repeat expansions. Therefore, our findings suggest that BAFME4 is caused by the insertions of the intronic TTTCA repeats in YEATS2. Interestingly, all four types of BAFMEs for which underlying genes have been found (BAFMEs 1, 4, 6 and 7) are caused by the same molecular pathology, suggesting that the insertions of non-coding TTTCA repeats are involved in their pathogenesis.

The most 5' truncating homozygous mutation of WNT1 in siblings with osteogenesis imperfecta with a variable degree of brain anomalies: a case report.

BACKGROUND: WNT1 mutations cause bone fragility as well as brain anomalies. There are some reported cases of WNT1 mutations with normal cognition. Genotype and phenotype correlation of WNT1 mutations has not been established. CASE PRESENTATION: Here we present two female siblings with osteogenesis imperfecta (OI) born to a consanguineous couple. Both sustained severe bone deformities. However, only the younger had severe brain anomalies resulting in an early death from pneumonia, while the older had normal intellectual development. Next generation sequencing showed a homozygous mutation, c.6delG, p.Leu3Serfs*36 in WNT1. To our knowledge, it is the most 5' truncating mutation to date. CONCLUSION: This report emphasizes the intrafamilial variability of brain anomalies found in this OI type and suggests that WNT1 may not be necessary for normal human cognitive development.

Cole-Carpenter syndrome in a patient from Thailand.

Cole-Carpenter syndrome (CCS), commonly classified as a rare type of osteogenesis imperfecta, is a disorder with severe bone fragility, craniosynostosis, and distinct facial features. Recently, the heterozygous missense mutation, c.1178A>G, p.Tyr393Cys, in exon 9 of P4HB which encodes protein disulfide isomerase, has been found in three Caucasian patients with CCS. Ethnic background is known to affect clinical manifestations, especially facial features of dysmorphic syndromes. Here, we describe the first Asian CCS patient possessing the recurrent mutation in P4HB. Although she had several common features of CCS including bulging forehead, ocular proptosis, midface hypoplasia, long bone deformity, popcorn epiphyses, vertebral fractures, and scoliosis, she did not have hydrocephalus, wormian bones, and dentinogenesis imperfecta, commonly seen in Caucasian patients. Interestingly, she is the only one without macrocephaly. Radiologically, metadiaphyseal fractures of the long bones with metaphyseal sclerosis were found, substantiating that they provide a definitive radiological feature of CCS. In addition, we showed for the first time a three-dimensional facial scan of a patient with CCS. She had been given intravenous bisphosphonate since the age of 9 months and had responded well. Our study presents the clinical features of the first Asian patient, supports metaphyseal scleroses and fractures as radiological clues, strengthens early bisphosphonate administration, and confirms the etiologic role of the c.1178A>G variant in P4HB across populations.

Massive parallel sequencing as a new diagnostic approach for phenylketonuria and tetrahydrobiopterin-deficiency in Thailand.

BACKGROUND: Hyperphenylalaninemia (HPA) can be classified into phenylketonuria (PKU) which is caused by mutations in the phenylalanine hydroxylase (PAH) gene, and BH4 deficiency caused by alterations in genes involved in tetrahydrobiopterin (BH4) biosynthesis pathway. Dietary restriction of phenylalanine is considered to be the main treatment of PKU to prevent irreversible intellectual disability. However, the same dietary intervention in BH4 deficiency patients is not as effective, as BH4 is also a cofactor in many neurotransmitter syntheses. METHOD: We utilized next generation sequencing (NGS) technique to investigate four unrelated Thai patients with hyperphenylalaninemia. RESULT: We successfully identified all eight mutant alleles in PKU or BH4-deficiency associated genes including three novel mutations, one in PAH and two in PTS, thus giving a definite diagnosis to these patients. Appropriate management can then be provided. CONCLUSION: This study identified three novel mutations in either the PAH or PTS gene and supported the use of NGS as an alternative molecular genetic approach for definite diagnosis of hyperphenylalaninemia, thus leading to proper management of these patients in Thailand.

Two novel compound heterozygous BMP1 mutations in a patient with osteogenesis imperfecta: a case report.

BACKGROUND: Osteogenesis imperfecta (OI) is a collagen-related bone dysplasia leading to a susceptibility to fractures. OI can be caused by mutations in several genes including BMP1. It encodes two isoforms, bone morphogenetic protein 1 (BMP1) and mammalian tolloid (mTLD); both have proteolytic activity to remove the C-propeptide from procollagen. CASE PRESENTATION: We report a Thai OI patient who had his first fracture at the age of three months. Using next generation sequencing, we successfully identified two novel compound heterozygous BMP1 mutations. One mutation, c.796_797delTT (p.Phe266Argfs*25) affects both BMP1 and mTLD isoforms, while the other, c.2108-2A > G, affects only the BMP1 isoform. Preservation of the mTLD may explain the relatively less severe clinical phenotype in this patient. Intravenous bisphosphonate was given from the age of 8 months to 5 years. He was free from fractures for 9 months before discontinuation. CONCLUSION: This case expands the mutation spectrum of BMP1, strengthens the correlation between genotype and phenotype, and supports the benefits of bisphosphonate in OI patients with BMP1 mutations.

Monoallelic FGFR3 and Biallelic ALPL mutations in a Thai girl with hypochondroplasia and hypophosphatasia.

Skeletal dysplasias are a complex group of more than 350 disorders with phenotypic and genotypic heterogeneity affecting bone and cartilage growth. We studied a 2-year-old girl and her 21-year-old mother with disproportionate short stature. In addition to typical features of hypochondroplasia found in both patients, the child had deformities of the extremity bones, metaphyseal flares, and bilateral transverse (Bowdler) fibular spurs with overlying skin dimples detected at birth. Intravenous pamidronate was started in the child since the age of 17 days, and then every two months. Exome sequencing revealed that the girl was heterozygous for a missense mutation (c.1651A>G, p.Ile538Val) in exon 13 of FGFR3, a known mutation for hypochondroplasia, inherited from her mother. Interestingly, the child also harbored compound heterozygous missense mutations in exon 12 of ALPL, c.1460C>T (p.Ala487Val) inherited from her mother and c.1479C>A (p.Asn493Lys) inherited from her healthy father. The former mutation was previously reported in perinatal hypophosphatasia while the latter was novel. Constantly reduced serum alkaline phosphatase levels including the one before the pamidronate administration and a substantially elevated level of plasma pyridoxal 5'-phosphate detected at age 28 months supported the diagnosis of hypophosphatasia. After a definite diagnosis was achieved, pamidronate was withdrawn at the age of 28 months. No adverse events were observed during pamidronate therapy. In conclusion, we describe a unique case with monoallelic FGFR3 and biallelic ALPL mutations leading to features of both hypochondroplasia and hypophosphatasia.

Short stature, platyspondyly, hip dysplasia, and retinal detachment: an atypical type II collagenopathy caused by a novel mutation in the C-propeptide region of COL2A1: a case report.

BACKGROUND: Heterozygous mutations in COL2A1 create a spectrum of clinical entities called type II collagenopathies that range from in utero lethal to relatively mild conditions which become apparent only during adulthood. We aimed to characterize the clinical, radiological, and molecular features of a family with an atypical type II collagenopathy. CASE PRESENTATION: A family with three affected males in three generations was described. Prominent clinical findings included short stature with platyspondyly, flat midface and Pierre Robin sequence, severe dysplasia of the proximal femora, and severe retinopathy that could lead to blindness. By whole exome sequencing, a novel heterozygous deletion, c.4161_4165del, in COL2A1 was identified. The phenotype is atypical for those described for mutations in the C-propeptide region of COL2A1. CONCLUSIONS: We have described an atypical type II collagenopathy caused by a novel out-of-frame deletion in the C-propeptide region of COL2A1. Of all the reported truncating mutations in the C-propeptide region that result in short-stature type II collagenopathies, this mutation is the farthest from the C-terminal of COL2A1.

A Frameshift Mutation in PEN-2 Causes Familial Comedones Syndrome.

BACKGROUND: Familial comedones without dyskeratosis are a rare autosomal dominant skin disorder, characterized by the occurrence of comedones that are distributed all over the body with specific features. We have previously reported two Thai families with familial comedones with expanded phenotypic spectrum. However, its genetic defect and pathogenesis remain unknown. OBJECTIVE: To explore the molecular defect causing familial comedones. METHODS: Whole-genome linkage analysis and whole-exome sequencing in family I were performed. RESULTS: We identified a heterozygous one-base pair insertion, c.84_85insT (p. L28FfsX93) in PEN-2, located within the linked region on chromosome 19. PCR-Sanger sequencing confirmed the identified mutation. The mutation segregated with the disease phenotype in family I and was fully penetrant. This similar mutation was also present in the unrelated affected individual from family II. Quantitative PCR revealed increased mRNA expression of PEN-2 in leukocytes of affected individuals. CONCLUSION: We for the first time identify PEN-2 as the causative gene of familial comedones.

Absent expression of the osteoblast-specific maternally imprinted genes, DLX5 and DLX6, causes split hand/split foot malformation type I.

BACKGROUND: Split hand/split foot malformation (SHFM) type 1 is characterised by missing central digital rays with clefts of the hands and/or feet, which was linked to chromosome 7q21.3. While double knockout of Dlx5 and Dlx6 resulted in limb defects in mice, the majority of patients with SHFM1 had only heterozygous chromosomal abnormalities. OBJECTIVE: To investigate the clinical and molecular features of a large family with SHFM1. METHODS: Blood samples of family members were investigated by linkage analysis, array comparative genomic hybridisation, exome sequencing and PCR-Sanger sequencing. Cultures from bone specimens obtained from the proband and an unrelated unaffected individual were established and subjected to quantitative real-time PCR, reverse-transcribed PCR, Western blot and imprinting analysis. RESULTS: We report a large pedigree of SHFM1 with 10 members having a heterozygous 103 kb deletion, the smallest one ever reported to be associated with SHFM1. Of these 10, two had no limb anomalies, making a penetrance of 80%. The deletion encompassed exons 15 and 17 of DYNC1I1, which are known enhancers of two downstream genes, DLX5 and DLX6. Surprisingly, DLX5 and DLX6 RNA and proteins in our proband's cultured osteoblasts, instead of 50% decrease, were absent. Allelic expression studies in cultured osteoblasts of the unaffected individual showed that DSS1, DLX6 and DLX5 expressed only paternal alleles. These lines of evidence indicate that DSS1, DLX6 and DLX5 were maternally imprinted in osteoblasts. CONCLUSIONS: SHFM1 in our family is caused by a heterozygous paternal deletion of enhancers of the osteoblast-specific maternally imprinted DLX6 and DLX5 genes, leading to the absence of their proteins.

ZRS 406A>G mutation in patients with tibial hypoplasia, polydactyly and triphalangeal first fingers.

Werner mesomelic syndrome (WMS), an autosomal dominant disorder characterized by hypoplastic tibiae, triphalangeal thumbs and polydactyly, is caused by a specific point mutation at the position 404 in zone of polarizing activity regulatory sequence (ZRS). Here we identified two additional families with WMS. All three patients in three generations of Family 1 were found to harbor the same heterozygous 406A>G mutation in ZRS. The fourth patient from Family 2 was a sporadic case with the known 404 point mutation. The novel 406A>G mutation expands mutational spectrum in ZRS causing WMS, provides evidence for a functionally important nucleotide position 406 of ZRS in humans and has implications for genetic counseling.

De novo genome assembly and transcriptome sequencing in foot and mantle tissues of Megaustenia siamensis reveals components of adhesive substances.

The semislug Megaustenia siamensis, commonly found in Thailand, is notable for its exceptional capacity to produce biological adhesives, enabling it to adhere to tree leaves even during heavy rainfall. In this study, we generated the first reference genome for M. siamensis using a combination of three sequencing technologies: Illumina's short-read, Pac-Bio's HIFI long-read, and Hi-C. The assembled genome size was 2593 billion base pairs (bp), containing 34,882 protein-coding genes. Our analysis revealed positive selection in pathways associated with the ubiquitin-proteasome system. Furthermore, RNA sequencing of foot and mantle tissues unveiled the primary constituents of the adhesive, including lectin-like proteins (C-lectin, H-lectin, and C1q) and matrilin-like proteins (VWA and EGF). Additionally, antimicrobial peptides were identified. The comprehensive M. siamensis genome and tissue-specific transcriptomic data provided here offer valuable resources for understanding its biology and exploring potential medical applications.

A novel BAG5 variant impairs the ER stress response pathway, causing dilated cardiomyopathy and arrhythmia.

Pathogenic BAG5 variants recently linked to dilated cardiomyopathy (DCM) prompt further investigation into phenotypic, mutational, and pathomechanistic aspects. We explored the clinical and molecular characteristics of DCM associated with BAG5 variants, uncovering the consistently severe manifestations of the disease and its impact on the endoplasmic reticulum (ER) stress response. The analysis involved three siblings affected by DCM and arrhythmia, along with their four unaffected siblings, their unaffected father, and their mother who exhibited arrhythmia. The parents were consanguineous. Exome and Sanger sequencing identified a novel BAG5 variant, c.444_445delGA (p.Lys149AsnfsTer6), homozygous in affected siblings and heterozygous in parents and unaffected siblings. We generated heterozygous and homozygous Bag5 point mutant knock-in (KI) mice and evaluated cardiac pathophysiology under stress conditions, including tunicamycin (TN) administration. Bag5-/- mice displayed no abnormalities up to 12 months old and showed no anomalies during an exercise stress test. However, following TN injection, Bag5-/- mice exhibited significantly reduced left ventricular fractional shortening (LVFS) and ejection fraction (LVEF). Their cardiac tissues exhibited a notable increase in apoptotic cells, despite non-distinctive changes in CHOP and GRP78 levels. Interestingly, only Bag5 KI male mice demonstrated arrhythmia, which was more pronounced in Bag5-/- than in Bag5+/-males. Here, our study reveals a novel BAG5 mutation causing DCM by impairing the ER stress response, with observed sex-specific arrhythmia differences.

Comprehensive genome assembly reveals genetic diversity and carcass consumption insights in critically endangered Asian king vultures.

The Asian king vulture (AKV), a vital forest scavenger, is facing globally critical endangerment. This study aimed to construct a reference genome to unveil the mechanisms underlying its scavenger abilities and to assess the genetic relatedness of the captive population in Thailand. A reference genome of a female AKV was assembled from sequencing reads obtained from both PacBio long-read and MGI short-read sequencing platforms. Comparative genomics with New World vultures (NWVs) and other birds in the Family Accipitridae revealed unique gene families in AKV associated with retroviral genome integration and feather keratin, contrasting with NWVs' genes related to olfactory reception. Expanded gene families in AKV were linked to inflammatory response, iron regulation and spermatogenesis. Positively selected genes included those associated with anti-apoptosis, immune response and muscle cell development, shedding light on adaptations for carcass consumption and high-altitude soaring. Using restriction site-associated DNA sequencing (RADseq)-based genome-wide single nucleotide polymorphisms (SNPs), genetic relatedness and inbreeding status of five captive AKVs were determined, revealing high genomic inbreeding in two females. In conclusion, the AKV reference genome was established, providing insights into its unique characteristics. Additionally, the potential of RADseq-based genome-wide SNPs for selecting AKV breeders was demonstrated.

Disorders with similar clinical phenotypes reveal underlying genetic interaction: SATB2 acts as an activator of the UPF3B gene.

Two syndromic cognitive impairment disorders have very similar craniofacial dysmorphisms. One is caused by mutations of SATB2, a transcription regulator and the other by heterozygous mutations leading to premature stop codons in UPF3B, encoding a member of the nonsense-mediated mRNA decay complex. Here we demonstrate that the products of these two causative genes function in the same pathway. We show that the SATB2 nonsense mutation in our patient leads to a truncated protein that localizes to the nucleus, forms a dimer with wild-type SATB2 and interferes with its normal activity. This suggests that the SATB2 nonsense mutation has a dominant negative effect. The patient's leukocytes had significantly decreased UPF3B mRNA compared to controls. This effect was replicated both in vitro, where siRNA knockdown of SATB2 in HEK293 cells resulted in decreased UPF3B expression, and in vivo, where embryonic tissue of Satb2 knockout mice showed significantly decreased Upf3b expression. Furthermore, chromatin immunoprecipitation demonstrates that SATB2 binds to the UPF3B promoter, and a luciferase reporter assay confirmed that SATB2 expression significantly activates gene transcription using the UPF3B promoter. These findings indicate that SATB2 activates UPF3B expression through binding to its promoter. This study emphasizes the value of recognizing disorders with similar clinical phenotypes to explore underlying mechanisms of genetic interaction.