Clinical and molecular characterization study of Chinese Kabuki syndrome in Hong Kong.

Kabuki syndrome (OMIM #147920 and 300867) is a rare genetic disorder characterized by a distinctive facial gestalt, intellectual disability and multiple congenital anomalies. We summarized the clinical features and molecular findings of the Kabuki syndrome (KS) patients diagnosed in Hong Kong between January 1991 and December 2019. There were 21 molecularly confirmed KS. Twenty of them were due to pathogenic KMT2D variants and one patient had KDM6A deletion. Nine KMT2D variants were novel. The clinical phenotype of our Chinese KS patients was largely comparable with that reported in patients of other ethnicities. This study expands the mutation spectrum but also provide important natural history information of Chinese KS in literature.

Prenatal phenotype of Kabuki syndrome: A case series and literature review.

OBJECTIVES: Kabuki syndrome (KS) is a genetic disorder characterized by intellectual disability, facial dysmorphism and congenital anomalies. We aim to investigate the prenatal features of fetuses with KS and to provide a comprehensive review of the literature on prenatal sonographic abnormalities associated with KS. METHODS: We retrospectively reviewed the prenatal ultrasound findings of all mothers of children with molecularly confirmed KS in Hong Kong, between 1991 and 2019. We also performed systematic review of the literature to identify studies on the prenatal findings in KS. RESULTS: We identified 11 cases with KS with detectable fetal ultrasound findings ranging from no detectable abnormalities to a variety of non-specific findings including increased nuchal translucency, pleural effusion, cardiac anomalies, renal anomalies, intrauterine growth restriction, polyhydramnios, oligohydramnios and single umbilical artery. In combining our cases with the 77 cases published, 42 (50.6%) of them had more than one abnormal antenatal ultrasound finding. The most frequent ultrasound features observed were cardiac anomalies (49.4%), followed by polyhydramnios (28.9%), genitourinary anomalies (26.5%), single umbilical artery (15.7%), intrauterine growth restriction (14.5%) and hydrops fetalis/pleural effusion/ascites (12.0%). CONCLUSIONS: These cases demonstrate the prenatal phenotypic heterogeneity associated with KS. Although the ultrasound abnormalities are non-specific, KS should be considered in the differential diagnosis when these fetal findings following normal microarray analysis/karyotyping.

Genetic landscape of RASopathies in Chinese: Three decades' experience in Hong Kong.

RASopathies are a group of genetic disorders due to dysregulation of the RAS-MAPK signaling pathway, which is important in regulating cell growth, proliferation, and differentiation. These include Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NSML), cardiofaciocutaneous (CFC) syndrome, and Costello syndrome (CS), clinical manifestations include growth retardation, developmental delay, cardiac defects, and specific dysmorphic features. There were abundant publications describing the genotype and phenotype from the Western populations. However, detailed study of RASopathies in Chinese population is lacking. We present here the largest cohort of RASopathies ever reported in Chinese populations, detailing the mutation spectrum and clinical phenotypes of these patients. The Clinical Genetic Service, Department of Health, and Queen Mary Hospital are tertiary referral centers for genetic disorders in Hong Kong. We retrospectively reviewed all the genetically confirmed cases of RASopathies, including NS, NSML, CFC syndrome, and CS, over the past 29 years (from 1989 to 2017). Analyses of the mutation spectrum and clinical phenotypes were performed. One hundred and ninety-one ethnic Chinese patients with genetically confirmed RASopathies were identified, including 148 patients with NS, 23 NSML, 12 CFC syndrome, and eight CS. We found a lower incidence of hypertrophic cardiomyopathy in individuals with NSML (27.3%), and NS caused by RAF1 mutations (62.5%). Another significant finding was for those NS patients with myeloproliferative disorder, the mutations fall within Exon 3 of PTPN11 but not only restricted to the well-known hotspots, that is, p.Asp61 and p.Thr731, which suggested that re-evaluation of the current tumor surveillance recommendation maybe warranted.

A novel missense mutation in CCDC88C activates the JNK pathway and causes a dominant form of spinocerebellar ataxia.

BACKGROUND: Spinocerebellar ataxias (SCAs) are a group of clinically and genetically diverse and autosomal-dominant disorders characterised by neurological deficits in the cerebellum. At present, there is no cure for SCAs. Of the different distinct subtypes of autosomal-dominant SCAs identified to date, causative genes for only a fraction of them are currently known. In this study, we investigated the cause of an autosomal-dominant SCA phenotype in a family that exhibits cerebellar ataxia and pontocerebellar atrophy along with a global reduction in brain volume. METHODS AND RESULTS: Whole-exome analysis revealed a missense mutation c.G1391A (p.R464H) in the coding region of the coiled-coil domain containing 88C (CCDC88C) gene in all affected individuals. Functional studies showed that the mutant form of CCDC88C activates the c-Jun N-terminal kinase (JNK) pathway, induces caspase 3 cleavage and triggers apoptosis. CONCLUSIONS: This study expands our understanding of the cause of autosomal-dominant SCAs, a group of heterogeneous congenital neurological conditions in humans, and unveils a link between the JNK stress pathway and cerebellar atrophy.

Congenital fibrosis of extraocular muscle type 1A due to KIF21A mutation: first case report from Hong Kong.

With the advancement of ophthalmological genetics, the molecular basis for more and more eye diseases can be elucidated. Congenital fibrosis of extraocular muscle (CFEOM) is an example. It is characterised by a congenital non-progressive restrictive ophthalmoplegia and ptosis. It is an autosomal dominant disease, caused by mutations of the KIF21A gene. With positive family history and typical ophthalmological findings, mutational analysis of KIF21A gene should be performed, not only to confirming the diagnosis, but also to offer a prognosis, for genetic counselling, and the possibility of prenatal diagnosis. Here we report the first KIF21A mutation associated with CFEOM1A in Hong Kong.

Oculopharyngeal muscular dystrophy: underdiagnosed disease in Hong Kong.

Despite the advances in the understanding of the molecular basis for oculopharyngeal muscular dystrophy in the last decade, it remains an underdiagnosed disease, especially among the Chinese. In the presence of a positive family history and late-onset ptosis, dysphagia, and proximal muscle weakness (its cardinal features), we suggest that PABPN1 gene analysis should be the first-line investigation to rule out this condition. Muscle biopsy can be reserved for atypical cases. Non-specific mitochondrial changes in the muscle specimens of these patients should be appreciated, so as to avoid diagnostic confusion. It is hoped that greater awareness among medical professionals and judicious use of PABPN1 gene analysis will lead to earlier diagnosis, better management, and avoidance of unnecessary invasive investigations of affected patients.

Deep neural network based quantum simulations and quasichemical theory for accurate modeling of molten salt thermodynamics.

With dual goals of efficient and accurate modeling of solvation thermodynamics in molten salt liquids, we employ ab initio molecular dynamics (AIMD) simulations, deep neural network interatomic potentials (NNIP), and quasichemical theory (QCT) to calculate the excess chemical potentials for the solute ions Na+ and Cl- in the molten NaCl liquid. NNIP-based molecular dynamics simulations accelerate the calculations by 3 orders of magnitude and reduce the uncertainty to 1 kcal mol-1. Using the Density Functional Theory (DFT) level of theory, the predicted excess chemical potential for the solute ion pair is -178.5 ± 1.1 kcal mol-1. A quantum correction of 13.7 ± 1.9 kcal mol-1 is estimated via higher-level quantum chemistry calculations, leading to a final predicted ion pair excess chemical potential of -164.8 ± 2.2 kcal mol-1. The result is in good agreement with a value of -163.5 kcal mol-1 obtained from thermo-chemical tables. This study validates the application of QCT and NNIP simulations to the molten salt liquids, allowing for significant insights into the solvation thermodynamics crucial for numerous molten salt applications.

Transferable Deep Learning Potential Reveals Intermediate-Range Ordering Effects in LiF-NaF-ZrF4 Molten Salt.

LiF-NaF-ZrF4 multicomponent molten salts are promising candidate coolants for advanced clean energy systems owing to their desirable thermophysical and transport properties. However, the complex structures enabling these properties, and their dependence on composition, is scarcely quantified due to limitations in simulating and interpreting experimental spectra of highly disordered, intermediate-ranged structures. Specifically, size-limited ab initio simulations and accuracy-limited classical models used in the past are unable to capture a wide range of fluctuating motifs found in the extended heterogeneous structures of liquid salt. This greatly inhibits our ability to design tailored compositions and materials. Here, accurate, efficient, and transferable machine learning potentials are used to predict structures far beyond the first coordination shell in LiF-NaF-ZrF4. Neural networks trained at only eutectic compositions with 29% and 37% ZrF4 are shown to accurately simulate a wide range of compositions (11-40% ZrF4) with dramatically different coordination chemistries, while showing a remarkable agreement with theoretical and experimental Raman spectra. The theoretical Raman calculations further uncovered the previously unseen shift and flattening of bending band at ∼250 cm-1 which validated the simulated extended-range structures as observed in compositions with higher than 29% ZrF4 content. In such cases, machine learning-based simulations capable of accessing larger time and length scales (beyond 17 Å) were critical for accurately predicting both structure and ionic diffusivities.

Further molecular and clinical delineation of the Wisconsin syndrome phenotype associated with interstitial 3q24q25 deletions.

Deletions of the distal 3q22.3 region encompassing the gene forkhead transcription factor FOXL2 (FOXL2) usually result in intellectual disability (ID) and the highly recognizable blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). We encountered three patients with molecularly defined interstitial deletions distal to the FOXL2 gene. They present with remarkably similar manifestations comprising variable ID, a coarse facial appearance, including prominent nose and eyebrows, hypogonadism and skin pigmentation abnormalities, and they share an approximately 8.8 Mb overlapping 3q24q25 deletion. Interestingly, one of the present patients was described previously in a clinical report with emphasis on her clinical similarity to the Wisconsin syndrome, suggesting that Wisconsin syndrome might be caused by a (micro) deletion within the 3q24q25 region.

Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potential.

Lithium-based molten salts have attracted significant attention due to their applications in energy storage, advanced fission reactors, and fusion devices. Lithium fluorides and particularly 66.6%LiF-33.3%BeF2 (Flibe) are of considerable interest in nuclear systems, as they show an excellent combination of favorable heat transfer, neutron moderation, and transmutation characteristics. For nuclear salts, the range of possible local structures, compositions, and thermodynamic conditions presents significant challenges in atomistic modeling. In this work, we demonstrate that atom-centered neural network interatomic potentials (NNIPs) provide a fast method for performing molecular dynamics of molten salts that is as accurate as ab initio molecular dynamics. For LiF, these potentials are able to accurately reproduce ab initio interactions of dimers, crystalline solids under deformation, crystalline LiF near the melting point, and liquid LiF at high temperatures. For Flibe, NNIPs accurately predict the structures and dynamics at normal operating conditions, high-temperature-pressure conditions, and in the crystalline solid phase. Furthermore, we show that NNIP-based molecular dynamics of molten salts are scalable to reach long time scales (e.g., nanosecond) and large system sizes (e.g., 105 atoms) while maintaining ab initio density functional theory accuracy and providing more than 3 orders of magnitude of computational speedup for calculating structure and transport properties.

Phenotypic features of carbohydrate sulfotransferase 3 (CHST3) deficiency in 24 patients: congenital dislocations and vertebral changes as principal diagnostic features.

We recently reported on the deficiency of carbohydrate sulfotransferase 3 (CHST3; chondroitin-6-sulfotransferase) in six subjects diagnosed with recessive Larsen syndrome or humero-spinal dysostosis [Hermanns et al. (2008); Am J Hum Genet 82:1368-1374]. Since then, we have identified 17 additional families with CHST3 mutations and we report here on a series of 24 patients in 23 families. The diagnostic hypothesis prior to molecular analysis had been: Larsen syndrome (15 families), humero-spinal dysostosis (four cases), chondrodysplasia with multiple dislocations (CDMD "Megarbane type"; two cases), Desbuquois syndrome (one case), and spondylo-epiphyseal dysplasia (one case). In spite of the different diagnostic labels, the clinical features in these patients were similar and included dislocation of the knees and/or hips at birth, clubfoot, elbow joint dysplasia with subluxation and limited extension, short stature, and progressive kyphosis developing in late childhood. The most useful radiographic clues were the changes of the lumbar vertebrae. Twenty-four different CHST3 mutations were identified; 16 patients had homozygous mutations. We conclude that CHST3 deficiency presents at birth with congenital dislocations of knees, hips, and elbows, and is often diagnosed initially as Larsen syndrome, humero-spinal dysostosis, or chondrodysplasia with dislocations. The incidence of CHST3 deficiency seems to be higher than assumed so far. The clinical and radiographic pattern (joint dislocations, vertebral changes, normal carpal age, lack of facial flattening, and recessive inheritance) is characteristic and distinguishes CHST3 deficiency from other disorders with congenital dislocations such as filamin B-associated dominant Larsen syndrome and Desbuquois syndrome.

Urinary incontinence should be added to the manifestation in women with Marfan syndrome.

INTRODUCTION AND HYPOTHESIS: We aimed to compare the incidence of urinary incontinence in women with Marfan syndrome and controls, hypothesizing that connective tissue abnormality could contribute to urinary incontinence. METHODS: A cross-sectional historical cohort study was conducted on 14 premenopausal women with Marfan syndrome and 534 controls using Urogenital Distress Inventory Short Form and Incontinence Impact Questionnaire Short Form. RESULTS: Marfan subjects had significantly higher incidence of urinary symptoms, stress urinary incontinence (SUI) and urge urinary incontinence (UUI) than controls (P = 0.02, P = 0.03, P = 0.02), despite their lower parity (P = 0.01). Direct logistic regression analysis indicated that Marfan syndrome, parity and age were associated with SUI; while Marfan syndrome was the only significant predictor of UUI. CONCLUSIONS: Premenopausal women with Marfan syndrome had a higher incidence of reported urinary symptoms. Urinary incontinence should be added to the list of clinical manifestations in women with Marfan syndrome.

Novel truncating mutations of the CHM gene in Chinese patients with choroideremia.

PURPOSE: Choroideremia (CHM) is an X-linked retinal degenerative disorder caused by mutations in the CHM gene. The mutations result in malfunction of the Rab escort protein 1 (REP-1). In this study, mutational analysis of the CHM gene was performed on five Chinese families clinically diagnosed with CHM. METHODS: Denaturing high performance liquid chromatography was used for mutation screening for all 15 exons and flanking intron regions of the CHM gene. Mutations were confirmed and characterized with DNA sequencing. Second samples were later collected for extraction of mRNA and proteins from leukocytes. A non-radioactive protein truncation test (PTT) was developed and used to characterize the truncating nature of the mutations. Immunoblot analysis of proteins extracted from leukocytes was also performed. RESULTS: Five mutations were identified in these five families, each with one distinct mutation: three frameshift, one nonsense, and one splicing. Two of these were novel mutations: c.627dupA in exon 5 and c.703-1G>C in intron 5. The truncating nature of the mutations was experimentally proved by PTT for four families with second samples collected. In particular, c.703-1G>C spliced exon 5 directly to exon 7 and deleted the entire exon 6 from the transcript. Direct immunoblot analysis failed to detect REP-1 in males affected by CHM, but demonstrated its presence in female carriers and homozygous normal females. CONCLUSIONS: This is the first study reporting mutations in the CHM gene in Chinese families. Mutational analysis was performed at the DNA, mRNA and protein levels. Five truncating mutations were found, and two of these were novel.

Molecular analysis of a chromosome 4 inversion segregating in a large schizophrenia kindred from Hong Kong.

The present study looks at a paracentric inversion on chromosome 4 [inv(4)(q13;q25)] in members of a large schizophrenia kindred from Hong Kong, and the possibility of a susceptibility gene for schizophrenia at one of the inversion breakpoints. Fluorescence in situ hybridization with BAC and fosmid clones was used to determine the location of the 4q13 and 4q25 breakpoints, however bioinformatic analysis indicated that no known genes are directly disrupted by the breakpoints. We identified several putative genes and expressed sequence tags (ESTs) from around the breakpoint regions, and have characterized them further in order to determine whether they may represent full-length mRNAs that are disrupted by the inversion. Overall, it appears that, while no known genes are disrupted, an as yet undiscovered gene, or indeed, a known gene, may be present near one of the breakpoints and may be disrupted by position effect. We hypothesized that either the 4q13 or 4q25 breakpoint region may contain a common susceptibility gene for schizophrenia. We genotyped 117 schizophrenia families for several short tandem repeat polymorphisms close to the breakpoints. Family based association testing showed no association at the 4q13 breakpoint region, but showed significant allelic association for marker D4S2989 at the 4q25 breakpoint region (p=0.016). This study suggests that the 4q breakpoint regions may harbour a gene that contributes to the illness in the large Hong Kong pedigree, and this 4q25 region should be examined further in other schizophrenia samples.

AGG interspersion analysis of the FMR1 CGG repeats in mental retardation of unspecific cause.

OBJECTIVES: To study the AGG interspersion pattern in mentally retarded patients of unspecified cause. METHODS: FMR1 CGG substructure in 104 normal and 232 mentally retarded (MR) males was determined by CGG repeat and AGG interspersion analyses. Genomic DNA of the study subjects was obtained for PCR and Southern hybridization analyses. RESULTS: All study subjects had less than 53 CGG repeats and none had fragile X syndrome of mental retardation. There was a significant difference (P < 0.006) in the AGG interspersion pattern. MR males had (1) more variable internal substructures, (2) proportionally less 2 and 3 AGG but more 0 and 1 AGG, less (CGG)(9)AGG(CGG)(9)AGG(CGG)(9) but more (CGG)(9)AGG(CGG)(19) alleles and (3) a longer pure 3' CGG repeat. CONCLUSIONS: Our results suggest that the MR alleles have a lesser number of interspersed AGG and a longer pure 3' CGG repeat than the normal population. They are thus more prone to instability and expansion to long repeat lengths as in the fragile X syndrome of mental retardation.

Detecting exon deletions and duplications of the DMD gene using Multiplex Ligation-dependent Probe Amplification (MLPA).

OBJECTIVES: To evaluate the efficacy of Multiplex Ligation-dependent Probe Amplification (MLPA) technique in comparison with the traditional multiplex PCR assay in detection of exon deletions and duplications of the DMD gene. DESIGN AND METHODS: The sensitivity and accuracy of MLPA were assessed and compared with the multiplex PCR in a total of 63 subjects including 43 subjects with Duchenne muscular dystrophy (DMD) or Becker muscular dystrophy (BMD) and 20 female carriers. RESULTS: MLPA was able to detect all the known deletions and duplications; it detected four additional mutations that had been missed by multiplex PCR. In addition, the extent of the deletions and duplications could be more accurately defined which in turn facilitated a genotype-phenotype correlation. CONCLUSIONS: MLPA is superior to multiplex PCR. It should be the method of choice for the detection of exon deletions and duplications of the DMD gene in patients with DMD or BMD, as well as in female carriers.

High rate of detection of subtelomeric aberration by using combined MLPA and subtelomeric FISH approach in patients with moderate to severe mental retardation.

OBJECTIVES: (1) To evaluate the prevalence of subtelomeric deletion in moderate to severe mental retardation population, (2) to assess the feasibility and cost-effectiveness of combined methodology in routine workup of this sub-population. METHOD: Twenty unrelated patients using strict selection criteria were recruited for the study from the Clinical Genetic Service. Patients were initially screened by Multiplex Ligation-dependent Probe Amplification (MLPA) for subtelomeric imbalance followed by FISH analysis for anatomical integrity. This is then followed by parental subtelomeric FISH analysis. RESULTS: Three subtelomeric deletions were identified. They were Deletion 1p36, Deletion 1q44 and Deletion 10q26; these were previously unidentified by conventional technique. CONCLUSIONS: The prevalence of subtelomeric deletion in our cohort of moderate to severe mental retardation patients is consistent with published findings of around 10%. The figure is on the higher side if more stringent criteria is used. The combination of strict clinical criteria, MLPA and selective subtelomeric FISH was shown to be feasible and cost-effective.

Triple-A syndrome--the first Chinese patient with novel mutations in the AAAS gene.

We report on the first Chinese patient with triple-A syndrome, who presented at 22 months with status epilepticus secondary to hyponatraemia and hypoglycaemia. Subsequent endocrine investigations confirmed primary adrenal insufficiency and aldosterone deficiency. In the presence of achalasia and alacrima, this patient satisfies the diagnostic criteria of triple-A syndrome. Further molecular testing detected compound heterozygous mutations in the AAAS gene: a c.580C --> T transition in exon 7 and a c.771delG single nucleotide deletion in exon 8. Testing of parents and brother confirmed their heterozygous carrier status.