Functional characterization of inactivating ABCC8 variants causing congenital hyperinsulinism.

Congenital hyperinsulinism (CHI; OMIM: 256450) is characterized by persistent insulin secretion despite severe hypoglycemia. The most common causes are variants in the ATP-binding cassette subfamily C member 8(ABCC8) and potassium inwardly-rectifying channel subfamily J member 11(KCNJ11) genes. These encode ATP-sensitive potassium (KATP) channel subunit sulfonylurea receptor 1 (SUR1) and inwardly rectifying potassium channel (Kir6.2) proteins. A 7-day-old male infant presented with frequent hypoglycemic episodes and was clinically diagnosed with CHI, underwent trio-whole-exome sequencing, revealing compound heterozygous ABCC8 variants (c.307C>T, p.His103Tyr; and c.3313_3315del, p.Ile1105del) were identified. In human embryonic kidney 293 (HEK293) and rat insulinoma cells (INS-1) transfected with wild-type and variant plasmids, KATP channels formed by p.His103Tyr were delivered to the plasma membrane, whereas p.Ile1105del or double variants (p.His103Tyr coupled with p.Ile1105del) failed to be transported to the plasma membrane. Compared to wild-type channels, the channels formed by the variants (p.His103Tyr; p.Ile1105del) had elevated basal [Ca2+]i, but did not respond to stimulation by glucose. Our results provide evidence that the two ABCC8 variants may be related to CHI owing to defective trafficking and dysfunction of KATP channels.

[Clinical manifestations and genetic analysis of 4 patients with variants of FBN1 gene].

OBJECTIVE: To explore the genetic basis for four patients suspected for Marfan syndrome (MFS). METHODS: Four male patients with suspected MFS and their family members who were treated at West China Second Hospital of Sichuan University from September 12, 2019 to March 27, 2021 were selected as the study subjects. Peripheral venous blood samples were collected from the patients and their parents or other pedigree members for the extraction of genomic DNA. Whole exome sequencing was carried out, and candidate variants were validated by Sanger sequencing. The pathogenicity of the variants was determined based on the guidelines from the American College of Medical Genetics and Genomics (ACMG). RESULTS: Genetic testing revealed that all four patients have harbored variants of the FBN1 gene, including c.430_433del (p.His144fs) deletional variant in exon 5, c.493C>T (p.Arg165*) nonsense variant in exon 6, c.5304_5306del (p.Asp1768del) deletional variant in exon 44 and c.5165C>G (p.Ser1722Cys) missense variant in exon 42. According to the ACMG guidelines, the c.430_433del and c.493C>T were classified as pathogenic variants (PVS1+PM2_Supporting+PP4; PVS1+PS1+PS2+PM2_Supporting+PP4). c.5304_5306del and c.5165C>G were classified as likely pathogenic variants (PS2+PM2_Supporting+PM4+PP4; PS2_Moderate+PS1+PM1+PM2_Supporting). CONCLUSION: The c.430_433del and c.5304_5306del variants of the FBN1 gene identified in this study were unreported previously. Above results have enriched the variation spectrum of the FBN1 gene and provided a basis for genetic counseling and prenatal diagnosis of patients with MFS and acromicric dysplasia.

NGS-based targeted sequencing identified two novel variants in Southwestern Chinese families with oculocutaneous albinism.

BACKGROUND: Oculocutaneous albinism (OCA) is a group of heterogeneous genetic diseases characterized by a reduction or complete lack of pigmentation in the hair, skin, and eyes. It is associated with reduced visual acuity, nystagmus, photophobia, and strabismus. OCA type 1 (OCA1) and type 2 (OCA2) are caused by mutations in the tyrosinase (TYR) and OCA2 genes, which are responsible for most cases of OCA. The present study aimed to identify the mutational spectra of 18 southwest Chinese probands with OCA. RESULTS: We used a skin disease-targeted panel to sequence more than 400 genes, including 23 genes (TYR, OCA2, AP3B1, BLOC1S3, BLOC1S6, C10orf11, DTNBP1, FRMD7, GPR143, HPS1, HPS3, HPS4, HPS5, HPS6, LYST, MC1R, MITF, MLPH, MYO5A, RAB27A, SLC24A5, SLC45A2, TYRP1) associated with syndromic and non-syndromic albinism. The targeted panel was applied to 18 patients from southwest China, nine (50%) patients were diagnosed with OCA1, and nine (50%) were diagnosed with OCA2. Our data indicate that OCA1 and OCA2, the most common subtypes, probably have the same prevalence in southwest China. In total, we identified 26 variants in TYR and OCA2 from 18 OCA cases using the NGS technology, including 24 variants presented in the Human Gene Mutation Database Professional (HGMD) and two novel variants, c.559_560insCATTATTATGTGTCAAATTATCCCC in TYR and c.1514 T > C in OCA2, which have not been previously reported. According to the American College of Medical Genetics and Genomics (ACMG) classification, c.559_560insCATTATTATGTGTCAAATTATCCCC (p.G190Cfs*12) is classified as a pathogenic variant, and c.1514 T > C (p.F505S) is evaluated as a likely pathogenic variant. CONCLUSIONS: Two novel variants were identified which will expand the mutational spectra of TYR and OCA2. The results of the present study may have implications for genetic counseling, carrier screening, and clinical management of the disease.

Ultrasound-guided transmuscular quadratus lumborum block reduced postoperative opioids consumptions in patients after laparoscopic hepatectomy: a three-arm randomized controlled trial.

BACKGROUND: To investigate whether transmuscular quadratus lumborum block (TQLB) combined with oxycodone-based patient-controlled intravenous analgesia (PCIA) compared with sufentanil-based patient-controlled intravenous analgesia could reduce postoperative pain and opioid consumption in patients undergoing laparoscopic hepatectomy. METHODS: Eighty patients undergoing laparoscopic hepatectomy surgery were randomly divided into Group S (Sufentanil for PCIA group), Group O (Oxycodone for PCIA group) and Group QO (transmuscular quadratus lumborum block + oxycodone for PCIA group). Primary outcome was Numerical Rating Scale (NRS) pain score when coughing at 6th hour after the operation. We summarized opioid consumption and recorded complications, opioid drug adverse reaction and analgesia satisfaction. RESULTS: NRS pain scores were significantly lower in Group QO while patients coughing at 6th hour after the operation compared with Group S and Group O (median (interquartile range [IQR]):Group S vs. Group O vs. Group QO 4.0 [3.0, 5.0] vs. 4.0[3.0,5.0]vs.3.0 [2.0, 3.0], p < 0.05). Within 24 h after surgery, the bolus times of PCIA (patient controlled intravenous analgesia) in the QO group was reduced which was compared with the Group S and Group O (median (interquartile range [IQR]):Group S vs. Group O vs. Group QO 13.0 [10.3, 19.5] vs. 11.5 [7.8, 18.3]vs.6.5[3.5,12.0], p < 0.05). The proportion of patients in the three groups who required additional analgesia was ranked as Group QO < Group O < Group S(p < 0.05). The analgesic satisfaction of patients in Group QO was higher than the Group S (p = 0.001) and Group O (p = 0.012). CONCLUSIONS: TQLB combined with oxycodone-based PCIA provided satisfactory postoperative analgesia and reduced oxycodone consumption in patients following laparoscopic hepatectomy. TRIAL REGISTRATION: ChiCTR1900028467 (22/12/2019).

Identification of a novel EXT2 frameshift mutation in a family with hereditary multiple exostoses by whole-exome sequencing.

BACKGROUND: Hereditary multiple exostoses (HME), also referred to as multiple osteochondromas, is an autosomal dominant skeletal disease characterized by the development of multiple overgrown benign bony tumors capped by cartilage and is associated with bone deformity, joint limitation, and short stature. Mutations in exostosin glycosyltransferase (EXT)1 and EXT2 genes, which are located on chromosomes 8q24.1 and 11p13, contribute to the pathogenesis of HME. METHODS: In the present study, a genetic analysis of a four-generation Chinese family with HME was conducted using whole-exome sequencing (WES), followed by validation using Sanger sequencing. RESULTS: A novel heterozygous frameshift mutation in exon 5 of EXT2 (c.944dupT, p.Leu316fs) was identified in all affected individuals but was not detected in any unaffected individuals. This mutation results in a frameshift that introduces a premature termination codon at position 318 (p.Leu316fs) with the ability to produce a truncated EXT2 protein that lacks the last 433 amino acids at its C-terminal to indicate a defective exostosin domain and the absence of the glycosyltransferase family 64 domain, or to lead to the degradation of mRNAs by nonsense-mediated mRNA decay, which is critical for the function of EXT2. CONCLUSION: Our results indicate that WES is effective in extending the EXT mutational spectra and is advantageous for genetic counseling and the subsequent prenatal diagnosis.

The red bayberry genome and genetic basis of sex determination.

Morella rubra, red bayberry, is an economically important fruit tree in south China. Here, we assembled the first high-quality genome for both a female and a male individual of red bayberry. The genome size was 313-Mb, and 90% sequences were assembled into eight pseudo chromosome molecules, with 32 493 predicted genes. By whole-genome comparison between the female and male and association analysis with sequences of bulked and individual DNA samples from female and male, a 59-Kb region determining female was identified and located on distal end of pseudochromosome 8, which contains abundant transposable element and seven putative genes, four of them are related to sex floral development. This 59-Kb female-specific region was likely to be derived from duplication and rearrangement of paralogous genes and retained non-recombinant in the female-specific region. Sex-specific molecular markers developed from candidate genes co-segregated with sex in a genetically diverse female and male germplasm. We propose sex determination follow the ZW model of female heterogamety. The genome sequence of red bayberry provides a valuable resource for plant sex chromosome evolution and also provides important insights for molecular biology, genetics and modern breeding in Myricaceae family.

[Application of copy number variation sequencing for prenatal diagnosis in women at an advanced maternal age].

OBJECTIVE: To assess the value of copy number variation analysis based on next generation sequencing (CNV-seq) in prenatal diagnosis for women at advanced maternal age. METHODS: A prospective analysis was carried out for women who underwent amniocentesis at 18~36 weeks of gestation for fetal CNV-seq for advanced maternal age. RESULTS: For 1461 unrelated Chinese women with a singleton pregnancy, CNV-seq was performed for all samples successfully. The proportion of chromosomal abnormalities was 2.3% (34/1461), of which 44.12% were submicroscopic copy number variations (<5 Mb). CONCLUSION: Pregnant women at an advanced maternal age should be informed for not only common trisomies but all pathogenic chromosomal aberrations. NGS was a sensitive and accurate approach for detecting CNVs.

Prospective chromosome analysis of 3429 amniocentesis samples in China using copy number variation sequencing.

BACKGROUND: Next-generation sequencing is emerging as a viable alternative to chromosome microarray analysis for the diagnosis of chromosome disease syndromes. One next-generation sequencing methodology, copy number variation sequencing, has been shown to deliver high reliability, accuracy, and reproducibility for detection of fetal copy number variations in prenatal samples. However, its clinical utility as a first-tier diagnostic method has yet to be demonstrated in a large cohort of pregnant women referred for fetal chromosome testing. OBJECTIVE: We sought to evaluate copy number variation sequencing as a first-tier diagnostic method for detection of fetal chromosome anomalies in a general population of pregnant women with high-risk prenatal indications. STUDY DESIGN: This was a prospective analysis of 3429 pregnant women referred for amniocentesis and fetal chromosome testing for different risk indications, including advanced maternal age, high-risk maternal serum screening, and positivity for an ultrasound soft marker. Amniocentesis was performed by standard procedures. Amniocyte DNA was analyzed by copy number variation sequencing with a chromosome resolution of 0.1 Mb. Fetal chromosome anomalies including whole chromosome aneuploidy and segmental imbalances were independently confirmed by gold standard cytogenetic and molecular methods and their pathogenicity determined following guidelines of the American College of Medical Genetics for sequence variants. RESULTS: Clear interpretable copy number variation sequencing results were obtained for all 3429 amniocentesis samples. Copy number variation sequencing identified 3293 samples (96%) with a normal molecular karyotype and 136 samples (4%) with an altered molecular karyotype. A total of 146 fetal chromosome anomalies were detected, comprising 46 whole chromosome aneuploidies (pathogenic), 29 submicroscopic microdeletions/microduplications with known or suspected associations with chromosome disease syndromes (pathogenic), 22 other microdeletions/microduplications (likely pathogenic), and 49 variants of uncertain significance. Overall, the cumulative frequency of pathogenic/likely pathogenic and variants of uncertain significance chromosome anomalies in the patient cohort was 2.83% and 1.43%, respectively. In the 3 high-risk advanced maternal age, high-risk maternal serum screening, and ultrasound soft marker groups, the most common whole chromosome aneuploidy detected was trisomy 21, followed by sex chromosome aneuploidies, trisomy 18, and trisomy 13. Across all clinical indications, there was a similar incidence of submicroscopic copy number variations, with approximately equal proportions of pathogenic/likely pathogenic and variants of uncertain significance copy number variations. If karyotyping had been used as an alternate cytogenetics detection method, copy number variation sequencing would have returned a 1% higher yield of pathogenic or likely pathogenic copy number variations. CONCLUSION: In a large prospective clinical study, copy number variation sequencing delivered high reliability and accuracy for identifying clinically significant fetal anomalies in prenatal samples. Based on key performance criteria, copy number variation sequencing appears to be a well-suited methodology for first-tier diagnosis of pregnant women in the general population at risk of having a suspected fetal chromosome abnormality.

Sudden Death in a Male Infant Due to Histiocytoid Cardiomyopathy: An Autopsy Case and Review of the Literature.

Histiocytoid cardiomyopathy (HC) is a very rare cardiac disorder that mainly affects female infants younger than 2 years. It may manifest as ventricular tachycardia or dilated cardiomyopathy and frequently causes sudden death. The most common grossly change is multifocal uneven thickening of the endocardium, presenting a yellowish color, with some area forming nodular appearance, and histologically featured by scattered clusters of histiocytoid myocytes under the endocardium. Here, we present a 19-month-old male infant who died of heart failure, and an autopsy was performed and confirmed the diagnosis of HC. We also reviewed the literature and focused on the research progression of the origin and genetic/molecular features of HC in recent years.

Identification of a novel LMX1B nonsense variant associated with congenital talipes equinovarus by prenatal exome sequencing: A case report.

BACKGROUND: Congenital talipes equinovarus (CTEV) is a rotational foot deformity that affects muscles, bones, connective tissue, and vascular or neurological tissues. The etiology of CTEV is complex and unclear, involving genetic and environmental factors. Nail-patella syndrome is an autosomal dominant disorder caused by variants of the LIM homeobox transcription factor 1 beta gene (LMX1B, OMIM:602575). LMX1B plays a key role in the development of dorsal limb structures, the kidneys, and the eyes, and variants in this gene may manifest as hypoplastic or absent patella, dystrophic nails, and elbow and iliac horn dysplasia; glomerulopathy; and adult-onset glaucoma, respectively. This study aimed to identify pathogenic variants in a fetus with isolated talipes equinovarus diagnosed by ultrasound in the second trimester, whose father exhibited dysplastic nails and congenital absence of bilateral patella. METHODS: Prenatal whole-exome sequencing (WES) of the fetus and parents was performed to identify the genetic variant responsible for the fetal ultrasound abnormality, followed by validation using Sanger sequencing. RESULTS: A novel heterozygous nonsense variant in exon 6 of LMX1B (c.844C>T, p.Gln282*) was identified in the fetus and the affected father but was not detected in any unaffected family members. This nonsense variant resulted in a premature termination codon at position 282, which may be responsible for the clinical phenotype through the loss of function of the gene product. CONCLUSIONS: Our study indicating that a fetus carrying a novel nonsense variant of LMX1B (c.844C>T, p.Gln282*) can exhibit isolated talipes equinovarus, which expands the LMX1B genotypic spectrum and is advantageous for genetic counseling.

RCAN family member 3 deficiency contributes to noncompaction of the ventricular myocardium.

Noncompaction of the ventricular myocardium (NVM), the third most diagnosed cardiomyopathy, is characterized by prominent trabeculae and intratrabecular recesses. However, the genetic etiology of 40%-60% of NVM cases remains unknown. Here, we identify two infants with NVM, in a nonconsanguineous family, with a typical clinical presentation of persistent bradycardia since the prenatal period. A homozygous missense variant (R223L) of RCAN family member 3 (RCAN3) is detected in both infants using whole-exome sequencing. In the zebrafish model, marked cardiac dysfunction is detected in rcan3 deficiency (MO-rcan3ATG-injected) and rcan-/- embryos. Developmental dysplasia of both endocardial and myocardial layers is also detected in rcan3-deficient embryos. RCAN3 R223L variant mRNAs can not rescue heart defects caused by rcan3 knockdown or knockout; however, hRCAN3 mRNAs rescue these phenotypes. RNA-seq experiments show that several genes involved in cardiomyopathies are significantly regulated through multiple signaling pathways in the rcan3-knockdown zebrafish model. In human cardiomyocytes, RCAN3 deficiency results in reduced proliferation and increased apoptosis, together with an abnormal mitochondrial ultrastructure. Thus, we suggest that RCAN3 is a susceptibility gene for cardiomyopathies, especially NVM and that the R223L mutation is a potential loss-of-function variant.

Synthesis of Carbon Dots with Hemostatic Effects Using Traditional Chinese Medicine as a Biomass Carbon Source.

As novel nanomaterials developed gradually with nanotechnology, carbon dots have been widely applied in medical applications, including disease treatment, drug delivery, antibacterial applications, and phototherapy. Based on the similar process between Chinese medicinal materials for hemostasis and modern carbon dots, this paper reports the preparation of four luminescent carbon dots with Chinese medicinal materials (plants and animals) as carbon sources and the investigation on their hemostatic effects in vitro and in rat bleeding models. It is found that the four studied carbon dots exhibit similar hemostatic effects and hemostatic mechanisms through impacting both endogenous and exogenous coagulation pathways. In addition, these carbon dots all exhibit anti-inflammatory effects and good biocompatibility, ensuring their potential in pretraumatic fields. This work provides a new perspective for hemostatic carbon dots prepared using carbonized natural plants and animals and new ideas for the research of new hemostatic materials.

Case Report: The compound heterozygotes variants in FLT4 causes autosomal recessive hereditary lymphedema in a Chinese family.

Background: Lymphedema is a local form of tissue swelling, which is caused by excessive retention of lymph fluid in interstitial compartment caused by impaired lymphatic drainage damage. Primary lymphedema is caused by developmental lymphatic vascular abnormalities. Most cases are inherited as autosomal dominant, with incomplete penetrance and variable expression. Here we report compound heterozygotes variants in FLT4 of a Chinese family associated with primary lymphedema display autosomal recessive inheritance. Case presentation: Trio-whole-exome sequencing (Trio-WES) was performanced to analyse the underlying genetic cause of a proband with primary lymphedema in a Chinese family. Sanger sequencing was used to validate the variants in proband with primary lymphedema and members of the family with no clinical signs and symptoms. We reported compound heterozygotes for the Fms Related Receptor Tyrosine Kinase 4 (FLT4) gene detected in the proband, who carrying two different point variants. One was a missense variant (NM_182925.5; c.1504G>A, p.Glu502Lys), and the other was a recurrent variant (NM_182925.5; c.3323_3325del, p.Phe1108del). The missense variant c.1504G>A was detected in the proband, unaffected father, and unaffected paternal grandmother but not detected in unaffected paternal grandfather. The recurrent variant c.3323_3325del was detected in the proband, unaffected mother, and unaffected maternal grandfather but not detected in unaffected maternal grandmother. Our results suggests the possibility of an autosomal recessive inherited form of primary lymphedema resulting from variants of FLT4 encoding the vascular endothelial growth factor receptor-3. Conclusion: The results of the present study identifed compound heterozygotes FLT4 variants in a family with primary lymphedema which provides more information for autosomal recessive primary lymphedema caused by FLT4.

Compound heterozygous splicing variants in KIAA0586 cause fetal short-rib thoracic dysplasia and cerebellar malformation: Use of exome sequencing in prenatal diagnosis.

BACKGROUND: Short-rib thoracic dysplasia (SRTD) and Joubert syndrome (JS) are rare genetic ciliopathies, and individuals with either syndrome can manifest cerebellar malformation and variable developmental delays. However, neither of these conditions is easily diagnosed during pregnancy due to a limited fetal phenotype. Here, we investigated a fetus that was initially observed to have short limbs and polydactyly and discovered a compound heterozygous pathogenesis through exome sequencing (ES). METHODS: Simultaneous trio-ES and chromosome microarray analysis was provided for the fetus. The presence and effects of these variants on splicing were further validated at the DNA and RNA levels. RESULTS: Only short limbs and post-axial polydactyly of the fetus were detected during the second trimester. Two variants (c.3940+1G>A and c.3303G>A), affecting splicing of KIAA0586, were identified from amniocytes through ES and validated by Sanger sequencing. More intensive fetal monitoring was applied, and the fetus was also found to have deformed cerebellar malformation and a constricted thoracic cage. CONCLUSIONS: Herein, we report the genetic pathogenesis of SRTD and/or JS associated with KIAA0586 in a fetus. The novel splicing variants observed expand the spectrum of KIAA0586 in SRTD and/or JS. Based on the genetic data and the distinct corresponding phenotypes discovered by imaging examination, a comprehensive diagnosis was made during pregnancy and more valuable prognostic information was provided for the parents.

L1 Syndrome Prenatal Diagnosis Supplemented by Functional Analysis of One L1CAM Gene Missense Variant.

L1 syndrome, a complex X-linked neurological disorder, is caused by mutations in the L1 cell adhesion molecule (L1CAM) gene. L1CAM molecule is a member of immunoglobulin (Ig) superfamily of neural cell adhesion molecules (CAMs), which plays a pivotal role in the developing nervous system. In this study, a L1CAM gene exonic missense variant (c.1108G > A, p.G370R) was identified in two induced fetuses (abnormal fetuses), who presented corpus callosum agenesis accompanied with hydrocephalus. Clinical data, published literature, online database, and bioinformatic analysis suggest that the single-nucleotide variant of L1CAM gene is a likely pathogenic mutation. In vitro assays were performed to evaluate the effects of this variant. Based on NSC-34/COS-7 cells transfected with wild-type (L1-WT) and mutated (L1-G370R) plasmids, the L1CAM gene exonic missense variant (c.1108G > A, p.G370R) reduced cell surface expression, induced partial endoplasmic reticulum retention, affected posttranslational modification, and reduced protein's homophilic adhesive ability, but did not induce endoplasmic reticulum stress, which might probably associate with L1 syndrome. Finally, 35 isolated fetuses were screened for L1CAM gene variants by Sanger sequencing. These cases all prenatally suspected of corpus callosum agenesis accompanied with hydrocephalus, which may relate to L1 syndrome. Consequently, one L1CAM gene single missense variant (c.550C > T, p.R184W) was detected in one fetus. Our results provided evidence that the L1CAM gene missense variant (c.1108G > A, p.G370R) may relate to L1 syndrome. The findings of this study suggest a potential possibility of L1CAM gene screening for prenatal diagnoses for fetuses presented corpus callosum agenesis accompanied with hydrocephalus.

A novel CLCNKB variant in a Chinese family with classic Bartter syndrome and prenatal genetic diagnosis.

BACKGROUND: Type III Bartter syndrome (BS), often known as classic Bartter syndrome is caused by variants in CLCNKB gene, which encoding the basolateral chloride channel protein ClC-Kb, and is characterized by renal salt wasting, hypokalemia, metabolic alkalosis, increased renin, and aldosterone levels. METHODS: A 2-year-old boy presented severe malnutrition, severe metabolic alkalosis and severe hypokalemia and was clinically diagnosed with BS. The trio exome sequencing (ES) was performed to discover the genetic cause of this patient, followed by validation using Sanger sequencing and quantitative polymerase chain reaction subsequently. RESULTS: The genetic analysis indicated that this patient with a compound heterozygous variants of CLCNKB gene including a novel nonsense variant c.876 T > A and a whole-gene deletion. The two variants were inherited from his parents, respectively. Subsequently, target sequencing of CLCNKB gene was performed for next pregnancy, and prenatal genetic diagnosis was provided for the family. CONCLUSIONS: The results of current study identified the compound heterozygous variants in a patient with classic BS. The novel variant expands the spectrum of CLCNKB variants in BS. Our study also indicates that ES is an alternative tool to simultaneously detect single-nucleotide variants and copy-number variants.

Carrying both COL1A2 and FBN2 gene heterozygous mutations results in a severe skeletal clinical phenotype: an affected family.

BACKGROUND: Osteogenesis imperfecta (OI) is the most common monogenic disease of the skeletal system and is usually caused by mutations in the COL1A1 or COL1A2 genes. Congenital contractural arachnodactyly syndrome (CCA) is an autosomal dominant hereditary disease of connective tissue. To date, the FBN2 gene is the only gene reported to cause CCA. Researchers found that COL1A2 and FBN2 are both involved in the extracellular matrix organization pathway. These findings suggest that these two genes play an important role in a similar mechanism and may trigger a synergistic effect. METHODS: Trio-whole-exome sequencing (Trio-WES) was performed to analyse the underlying genetic cause of a proband with OI in a Chinese family. Sanger sequencing was used to validate the mutations in 3 members of the family with OI with varying degrees of severity of skeletal abnormalities and the members with no clinical signs. RESULT: A c.3304G > C mutation in the COL1A2 gene (p.Gly1102Arg) and a novel c.4108G > T mutation in the FBN2 gene (p.Glu1370*) were detected in the proband, an affected member of the family. The affected individuals with both mutations present a more severe phenotype, while affected individuals present a milder phenotype if only the mutation in COL1A2 is detected (c.3304G > C). The unaffected individual in this family did not have any mutations in the COL1A2 gene or FBN2 gene. CONCLUSION: Our study is the first clinical report to indicate that patients carrying concomitant mutations in both the COL1A2 and FBN2 genes may present with more severe skeletal abnormalities. Furthermore, our study suggests the possibility of synergistic effects between the COL1A2 and FBN2 genes.

A novel USH2A variant in a patient with hearing loss and prenatal diagnosis of a familial fetus: a case report.

BACKGROUND: Usher syndrome (USH) is the most common cause of inherited deaf-blindness. The current study aimed to identify pathogenic variants in a Chinese patient with hearing loss and to report the identification of a novel p.(Phe1583Leufs*10) variant in USH2A, which met the needs of prenatal diagnosis of the patient's mother. CASE PRESENTATION: Genomic DNA obtained from a five-year-old girl with hearing loss was analyzed via the hearing loss-targeted gene panels. We identified the compound heterozygous variants c.8559-2A>G and c.4749delT in Usher syndrome type 2A (USH2A) gene as the underlying cause of the patient; the former variation has been reported in the literature, but not the latter. The parents of the girl were heterozygous carriers. The two variants were classified as pathogenic. Based on these findings, amniotic fluid samples were used for prenatal diagnosis of the couple's fetus, which was found to carry c.4749delT but not c.8559-2A>G variation. During the follow-up period of more than 9 months after the birth of the fetus, it was confirmed that the infant was healthy. CONCLUSIONS: The results of the present study identified two compound heterozygous USH2A variants in a patient with hearing loss and reported a novel USH2A variant which expands the spectrum of USH2A variants in USH.