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.

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.

A novel heterozygous PKD1 variant causing alternative splicing in a Chinese family with autosomal dominant polycystic kidney disease.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by pathogenic variants of PKD1 and PKD2. Compared to PKD2-related patients, patients with PKD1 pathogenic variants have more severe symptoms, present a gradual decline in renal function, and finally progress to end-stage kidney disease with an earlier mean onset age. METHODS: In this study, trio exome sequencing (ES) was performed to reveal the genetic etiology in a Chinese family clinically diagnosed with polycystic kidney, followed by validation through Sanger sequencing on both genomic DNA and cDNA levels. Subsequently, targeted preimplantation genetic testing was provided for the family. RESULTS: A novel heterozygous PKD1 variant (c.1717_1722+11del) was detected in the proband and other clinically-affected relatives. Interestingly, cDNA sequencing demonstrated that the variant, despite being annotated as non-frameshift within exon 8, impacted the splicing of PKD1. Two abnormal transcription products were formed: one induced frameshift, while the other caused 133 amino acids to be inserted between exon 8 and exon 9. CONCLUSIONS: Our study revealed a novel PKD1 variant using ES as the cause of ADPKD in a Chinese family with multiple affected members. The variant at the exon-intron boundary would induce alternative splicing, which should not be excluded from genetic analysis. Validated on the cDNA level could provide more comprehensive genetic information for disease stratification. And the novel variant expands the spectrum of PKD1 variants in ADPKD. The recurrent risk could be blocked accordingly for the families' offspring.

Case report: A novel de novo deletion mutation of DYRK1A is associated with intellectual developmental disorder, autosomal dominant 7.

Background: Intellectual developmental disorder 7 (also named DYRK1A syndrome) is an autosomal dominant disease. The main clinical features of DYRK1A syndrome include intellectual disability, microcephaly, and developmental delay. This study aimed to identify pathogenic variants in a Chinese girl with developmental delay, impaired social interaction, and autistic behavior. Case presentation: The case was a 6-year-old girl. Clinical symptoms of the patient mainly included developmental delay, seizures, autistic behavior and impaired social interaction. The patient presented with microcephaly, bushy eyebrows, a short lingual frenum, binocular esotropia, bilateral valgus and external rotation, and walked with an abnormal gait. Using whole-exome sequencing, we identified a 9,424 bp de novo heterozygous deletion (containing coding exons 10, 11, and 12, and partial sequences of non-coding exon 12) in DYRK1A, which is responsible for DYRK1A syndrome. The DYRK1A variant is classified as pathogenic according to the criteria of the American College of Medical Genetics and Genomics. Conclusions: The findings of this study augment the data regarding the pathogenic variants of DYRK1A and provide important information for molecular diagnosis.

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.

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.

Single-cell RNA sequencing of subcutaneous adipose tissues identifies therapeutic targets for cancer-associated lymphedema.

Cancer-associated lymphedema frequently occurs following lymph node resection for cancer treatment. However, we still lack effective targeted medical therapies for the treatment or prevention of this complication. An in-depth elucidation of the cellular alterations in subcutaneous adipose tissues of lymphedema is essential for medical development. We performed single-cell RNA sequencing of 70,209 cells of the stromal vascular fraction of adipose tissues from lymphedema patients and healthy donors. Four subpopulations of adipose-derived stromal cells (ASCs) were identified. Among them, the PRG4+/CLEC3B+ ASC subpopulation c3 was significantly expanded in lymphedema and related to adipose tissue fibrosis. Knockdown of CLEC3B in vitro could significantly attenuate the fibrogenesis of ASCs from patients. Adipose tissues of lymphedema displayed a striking depletion of LYVE+ anti-inflammatory macrophages and exhibited a pro-inflammatory microenvironment. Pharmacological blockage of Trem1, an immune receptor predominantly expressed by the pro-inflammatory macrophages, using murine LR12, a dodecapeptide, could significantly alleviate lymphedema in a mouse tail model. Cell-cell communication analysis uncovered a perivascular ligand-receptor interaction module among ASCs, macrophages, and vascular endothelial cells. We provided a comprehensive analysis of the lineage-specific changes in the adipose tissues from lymphedema patients at a single-cell resolution. CLEC3B was found to be a potential target for alleviating adipose tissue fibrosis. Pharmacological blockage of TREM1 using LR12 could serve as a promising medical therapy for treating lymphedema.

A novel deletion mutation in the BCOR gene is associated with oculo-facio-cardio-dental syndrome: a case report.

BACKGROUND: Oculo-facio-cardio-dental syndrome is a rare X-linked dominant syndrome, characterized by radiculomegaly, congenital cataracts, dysmorphic facial features, and congenital heart disease. Because of the rarity, this syndrome could be misdiagnosed by the clinician, especially for the infant who may present only one to two systems involved. CASE PRESENTATION: Here we report a 3-month-old female infant presenting with typical clinical manifestations of oculo-facio-cardio-dental syndrome, like ocular, facial, cardiac, and skeletal abnormalities, and the genetic analyses of the proband and her parents were provided. Genetic evaluations were completed using whole exon sequencing, which revealed a novel heterozygous mutation between exons 7 and 14 of the BCOR gene(OMIM:300485) in this patient but not in her parents. This mutation is likely to encode a premature stop codon producing a truncated protein. Our patient was diagnosed early enough to allow for the cardiac defects to be treated first, and she will be closely followed up to ensure that any new presentations are treated in a timeous manner. CONCLUSION: This patient fits the diagnostic criteria for oculo-facio-cardio-dental syndrome and is the youngest oculo-facio-cardio-dental syndrome patient ever reported, which is most important for her prognosis. In addition, this manuscript also describes a novel potenitally causative mutation for this syndrome.

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.

Transcriptome analysis and functional identification of adipose-derived mesenchymal stem cells in secondary lymphedema.

BACKGROUND: Secondary lymphedema is a common condition that affects patients with malignant tumors. Conservative treatments fail to provide lasting relief because they do not address the underlying pathological accumulation of excessive fat. Our aim is to clarify the molecular mechanisms of abnormal adipogenic differentiation in lymphedema adipose tissue. METHODS: We compared the proliferation and adipogenesis potential of adipose-derived mesenchymal stem cells (ASCs) from the lymphedema adipose tissue from liposuction specimens of 10 patients with extremity lymphedema with that of ASCs from adipose tissue from the normal upper abdomen of the same patients. Transcriptome analysis were performed to identify the differences between the two kinds of ASCs. Cyclin-dependent kinase 1 (CDK1) inhibitors were used to treat the abnormal ASCs in lymphedema adipose tissue. RESULTS: Our results demonstrate that significant functional and transcriptomic differences exist between the two kinds of ASCs. Up-regulated genes were mainly involved in cell proliferation and division while down-regulated genes were mainly associated with immune responses and inflammatory as well as osteogenic and myogenic differentiation. Furthermore, we find that the excessive proliferation and adipogenesis of ASCs from lymphedema adipose tissue returned to the normal phenotype by CDK1 inhibitors. ASCs from lymphedema adipose tissues have higher immunosuppressive effect and the cytokines related to immunosuppressive was significantly up-regulated. CONCLUSIONS: In conclusion, lymphedema-associated ASCs had more rapid proliferation and a higher adipogenic differentiation capacity. CDK1 may be a key driver of proliferation and adipogenic differentiation in these cells, which might expound the accumulation of adipose tissue extensively observed in secondary lymphedema. ASCs from lymphedema adipose tissues showed immunomodulation dysfunction and immunomodulation may play an important role in the pathogenesis of lymphedema.

Exosomal miR-423-5p mediates the proangiogenic activity of human adipose-derived stem cells by targeting Sufu.

BACKGROUND: Human adipose-derived stem cells (hADSCs) are an important source of cells for regenerative medicine. Evidence of extensive interactions with the surrounding microenvironment has led researchers to focus more on hADSCs as activating agents of regenerative pathways, rather than simply replacing damaged cells. Several studies have found that functional miRNAs can be packaged into exosomes and transferred from donor cells into recipient cells, indicating that transported miRNAs may be a new class of cell-to-cell regulatory species. The aim of the present study was to evaluate whether the exosome-derived miRNAs secreted by hADSCs are capable of influencing angiogenesis, a key step in tissue regeneration. METHODS: Exosomes were purified from hADSCs followed by the characterization of their phenotype and angiogenic potential in vitro. RNA sequencing was performed to detect the miRNAs that were enriched in the hADSC-derived exosomes. A miRNA-mimic experiment was used to detect the key miRNAs in the proangiogenic activity of hADSC-derived exosomes. RESULTS: Exosomes isolated from hADSCs were characterized as round membrane vesicles with a size of approximately 100 nm and were positive for CD9 and flotillin. The exosomes were internalized by primary human umbilical vein endothelial cells (HUVECs) and stimulated HUVEC proliferation and migration. Remarkably, the exosomes promoted vessel-like formation by HUVECs in a dose-dependent manner, and their maximum activity (10 µg/mL) was comparable with that of 5% FBS. The RNA-seq bioinformatics analysis predicted 1119 gene targets of the top 30 exosomal miRNAs in Gene Ontology (GO) analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis, and the pathway involved in the angiogenesis was among the top KEGG pathways. Moreover, intact miR-423-5p was further demonstrated to be transferred into HUVECs via exosomes and to exert its angiogenic function by targeting Sufu. CONCLUSIONS: Exosomal miR-423-5p mediated the proangiogenic activity of hADSCs by targeting Sufu, which may contribute to the exploitation of exosomes from hADSCs as a therapeutic tool for regenerative medicine.

Single-cell RNA-seq of cultured human adipose-derived mesenchymal stem cells.

Adipose-derived mesenchymal stem cells (ADSCs) show considerable promise for clinical applications in regenerative medicine. We performed a large-scale single-cell transcriptomic sequencing of 24,358 cultured human ADSCs from three donors. We provide a high-quality dataset, which would be a valuable resource for dissecting the intrapopulation heterogeneity of cultured ADSCs as well as interrogating lineage priming patterns for any interested lineages at single-cell resolution.

Thrombin-activated platelet-derived exosomes regulate endothelial cell expression of ICAM-1 via microRNA-223 during the thrombosis-inflammation response.

Platelet activation and endothelial damage play essential roles in atherosclerosis. The pathophysiology of this process is mediated by chemokines and exosomes, two critical players in cell communication. Thrombin-activated platelet-derived exosomes have protective effects on atherosclerosis and endothelial inflammation. To confirm these findings, we isolated exosomes using differential ultracentrifugation and transmission electron microscopy. The exosomes were identified using NanoSight-tracking analysis. Immunofluorescence staining and western blotting were performed to assess exosome uptake and intercellular adhesion molecule-1 (ICAM-1) expression in human umbilical vein endothelial cells (HUVECs). We found that the levels of miR-223, miR-339 and miR-21 were elevated in thrombin-activated platelet exosomes. This finding was verified in our atherosclerosis mouse model. We also found that miR-223 transfection in HUVECs inhibited ICAM-1 expression under TNF-α stimulation. Furthermore, the miR-223 inhibitor blocked the downregulating effects of exosomes on ICAM-1 expression. We examined the key proteins of two classical signaling pathways, MAPK and NF-κB, and found that miR-223 inhibited the phosphorylation of p38, JNK and ERK and blocked the nuclear translocation of NF-κB p65. Our results suggest that thrombin-activated platelet-derived exosomes inhibit ICAM-1 expression during inflammation. MiR-223 may mediate this process via regulation of the NF-κB and MAPK pathways.