Two Novel Variants of the CAPN3 Gene in Chinese Patients with Limb-Girdle Muscular Dystrophy Recessive 1.

INTRODUCTION: Recessive mutations in the CAPN3 gene can lead to limb-girdle muscular dystrophy recessive 1 (LGMD R1). Targeted next-generation sequencing facilitates the discovery of new mutations linked with disease, owing to its ability to selectively enrich specific genomic regions. METHODS: We performed targeted next-generation sequencing of all exons of the CAPN3 gene in 4 patients with sporadic limb-girdle muscular dystrophy (LGMD) and further analyzed the effects of the novel identified variant using various software tools. RESULTS: We found 5 variants in CAPN3 gene in 4 patients, c.82_83insC (insertion mutation) and c.1115+2T>C (splicing mutation) are reported for the first time in CAPN3 (NM_000070.2). The bioinformatics analysis indicated that these two novel variants affected CAPN3 transcription as well as translation. DISCUSSION: Our findings reveal previously unreported splicing mutation and insertion mutation in CAPN3 gene, further expanding the pathogenic gene profile of LGMD.

Interpretable prioritization of splice variants in diagnostic next-generation sequencing.

A critical challenge in genetic diagnostics is the computational assessment of candidate splice variants, specifically the interpretation of nucleotide changes located outside of the highly conserved dinucleotide sequences at the 5' and 3' ends of introns. To address this gap, we developed the Super Quick Information-content Random-forest Learning of Splice variants (SQUIRLS) algorithm. SQUIRLS generates a small set of interpretable features for machine learning by calculating the information-content of wild-type and variant sequences of canonical and cryptic splice sites, assessing changes in candidate splicing regulatory sequences, and incorporating characteristics of the sequence such as exon length, disruptions of the AG exclusion zone, and conservation. We curated a comprehensive collection of disease-associated splice-altering variants at positions outside of the highly conserved AG/GT dinucleotides at the termini of introns. SQUIRLS trains two random-forest classifiers for the donor and for the acceptor and combines their outputs by logistic regression to yield a final score. We show that SQUIRLS transcends previous state-of-the-art accuracy in classifying splice variants as assessed by rank analysis in simulated exomes, and is significantly faster than competing methods. SQUIRLS provides tabular output files for incorporation into diagnostic pipelines for exome and genome analysis, as well as visualizations that contextualize predicted effects of variants on splicing to make it easier to interpret splice variants in diagnostic settings.

CONGENITAL ADRENAL HYPERPLASIA WITH COMPOUND HETEROZYGOUS I2 SPLICE AND P453S MUTATIONS.

Background: Congenital adrenal hyperplasia (CAH) is an autosomal recessive inherited disorder caused by congenital deficiency of enzymes involved in cortisol biosynthesis from cholesterol in the adrenal cortex. In this article, we aimed to present a 29-year-old female patient with I2 splice point mutation detected in one allele and P453S mutation on the other allele of CYP21A2 gene associated with 21-hydroxylase deficiency. Her further investigation revealed that her mother had P453S mutation and her father had I2 splice mutation. Case report: A 29-year-old woman with CAH was admitted to our clinic with the request of pregnancy. Her physical examination revealed a height of 151 cm, weight 59 kg, body mass index 25.8 kg/m2. According to Tanner staging, she had Stage 3 breast development and pubic hair. Her laboratory test results were as follows: Glucose: 79 mg/dL (70-100 mg/dL), Creatinine: 0.6 (0.5-0.95 mg/dL), Sodium: 138 mEq/L (135-145 mEq/L), Potassium: 4.4 mEq/L (3.5-5.1 mEq/L), Cortisol: 0.05 µg/dL, ACTH: <5.00 pg/mL (5-46 pg/mL), 17-OH progesterone: 7.67 ng/mL (0-3 ng/mL). Chromosome analysis revealed a 46, XX karyotype. CYP21A2 gene mutation analysis was performed for the patient whose clinical history and laboratory results were compatible with congenital adrenal hyperplasia. During the reverse dot blot analysis, I2 splice mutation in one allele and P453S mutation in the other allele were detected. Conclusion: Although the I2 splice mutation detected in our case was mostly associated with a salt-wasting form of CAH, it was thought that the other P453S mutation detected may explain the relatively good clinical course in our case.

Personalized Development of Antisense Oligonucleotides for Exon Skipping Restores Type XVII Collagen Expression in Junctional Epidermolysis Bullosa.

Intermediate junctional epidermolysis bullosa caused by mutations in the COL17A1 gene is characterized by the frequent development of blisters and erosions on the skin and mucous membranes. The rarity of the disease and the heterogeneity of the underlying mutations renders therapy developments challenging. However, the high number of short in-frame exons facilitates the use of antisense oligonucleotides (AON) to restore collagen 17 (C17) expression by inducing exon skipping. In a personalized approach, we designed and tested three AONs in combination with a cationic liposomal carrier for their ability to induce skipping of COL17A1 exon 7 in 2D culture and in 3D skin equivalents. We show that AON-induced exon skipping excludes the targeted exon from pre-mRNA processing, which restores the reading frame, leading to the expression of a slightly truncated protein. Furthermore, the expression and correct deposition of C17 at the dermal-epidermal junction indicates its functionality. Thus, we assume AON-mediated exon skipping to be a promising tool for the treatment of junctional epidermolysis bullosa, particularly applicable in a personalized manner for rare genotypes.

AG-exclusion zone revisited: Lessons to learn from 91 intronic NF1 3' splice site mutations outside the canonical AG-dinucleotides.

Uncovering frequent motives of action by which variants impair 3' splice site (3'ss) recognition and selection is essential to improve our understanding of this complex process. Through several mini-gene experiments, we demonstrate that the pyrimidine (Y) to purine (R) transversion NM_000267.3(NF1):c.1722-11T>G, although expected to weaken the polypyrimidine tract, causes exon skipping primarily by introducing a novel AG in the AG-exclusion zone (AGEZ) between the authentic 3'ss AG and the branch point. Evaluation of 90 additional noncanonical intronic NF1 3'ss mutations confirmed that 63% of all mutations and 89% (49/55) of the single-nucleotide variants upstream of positions -3 interrupt the AGEZ. Of these AGEZ-interrupting mutations, 24/49 lead to exon skipping suggesting that absence of AG in this region is necessary for accurate 3'ss selection already in the initial steps of splicing. The analysis of 91 noncanonical NF1 3'ss mutations also shows that 90% either introduce a novel AG in the AGEZ, cause a Y>R transversion at position -3 or remove ≥2 Ys in the AGEZ. We confirm in a validation cohort that these three motives distinguish spliceogenic from splice-neutral variants with 85% accuracy and, therefore, are generally applicable to select among variants of unknown significance those likely to affect splicing.

CAP2 mutation leads to impaired actin dynamics and associates with supraventricular tachycardia and dilated cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy (DCM) is a primary myocardial disease leading to contractile dysfunction, progressive heart failure and excessive risk of sudden cardiac death. Around half of DCM cases are idiopathic, and genetic factors seem to play an important role. AIM: We investigated a possible genetic cause of DCM in two consanguineous children from a Bedouin family. METHODS AND RESULTS: Using exome sequencing and searching for rare homozygous variations, we identified a nucleotide change in the donor splice consensus sequence of exon 7 in CAP2 as the causative mutation. Using patient-derived fibroblasts, we demonstrated that the mutation causes skipping of exons 6 and 7. The resulting protein is missing 64 amino acids in its N-CAP domain that should prevent its correct folding. CAP2 protein level was markedly reduced without notable compensation by the homolog CAP1. However, ß-actin mRNA was elevated as demonstrated by real-time qPCR. In agreement with the essential role of CAP2 in actin filament polymerization, we demonstrate that the mutation affects the kinetics of repolymerization of actin in patient fibroblasts. CONCLUSIONS: This is the first report of a recessive deleterious mutation in CAP2 and its association with DCM in humans. The clinical phenotype recapitulates the damaging effects on the heart observed in Cap2 knockout mice including DCM and cardiac conduction disease, but not the other effects on growth, viability, wound healing and eye development. Our data underscore the importance of the proper kinetics of actin polymerization for normal function of the human heart.

Identification of a novel splice mutation in CTNNB1 gene in a Chinese family with both severe intellectual disability and serious visual defects.

The CTNNB1 gene encode the ß-catenin protein which is a core unit of the cadherin/catenin multiprotein complex. The loss-of-function mutation of the CTNNB1 gene recently has been confirmed as a cause of intellectual disability. Previous studies have found that patients with CTNNB1 gene mutation may have other clinical manifestation such as microcephaly, abnormal facial features, motor and language delays, and mild visual defects. Here, we reported a 27-year-old Chinese pregnant woman with a severe intellectual disability and serious visual defects who was detected with a novel splice mutation (c.734+1G>A) in CTNNB1 gene by whole-exome sequencing and confirmed by Sanger sequencing. Further investigation showed that the variant was inherited from her mother with similar phenotypes. This report not only helps to expand the mutant spectrum of the CTNNB1 gene but also prompts a new insight into genetic diagnosis in patients with both serious intellectual disability and visual defects.

Splicing defect in FKBP10 gene causes autosomal recessive osteogenesis imperfecta disease: a case report.

BACKGROUND: Osteogenesis imperfecta (OI) is a group of connective tissue disorder caused by mutations of genes involved in the production of collagen and its supporting proteins. Although the majority of reported OI variants are in COL1A1 and COL1A2 genes, recent reports have shown problems in other non-collagenous genes involved in the post translational modifications, folding and transport, transcription and proliferation of osteoblasts, bone mineralization, and cell signaling. Up to now, 17 types of OI have been reported in which types I to IV are the most frequent cases with autosomal dominant pattern of inheritance. CASE PRESENTATION: Here we report an 8- year- old boy with OI who has had multiple fractures since birth and now he is wheelchair-dependent. To identify genetic cause of OI in our patient, whole exome sequencing (WES) was carried out and it revealed a novel deleterious homozygote splice acceptor site mutation (c.1257-2A > G, IVS7-2A > G) in FKBP10 gene in the patient. Then, the identified mutation was confirmed using Sanger sequencing in the proband as homozygous and in his parents as heterozygous, indicating its autosomal recessive pattern of inheritance. In addition, we performed RT-PCR on RNA transcripts originated from skin fibroblast of the proband to analyze the functional effect of the mutation on splicing pattern of FKBP10 gene and it showed skipping of the exon 8 of this gene. Moreover, Real-Time PCR was carried out to quantify the expression level of FKBP10 in the proband and his family members in which it revealed nearly the full decrease in the level of FKBP10 expression in the proband and around 75% decrease in its level in the carriers of the mutation, strongly suggesting the pathogenicity of the mutation. CONCLUSIONS: Our study identified, for the first time, a private pathogenic splice site mutation in FKBP10 gene and further prove the involvement of this gene in the rare cases of autosomal recessive OI type XI with distinguished clinical manifestations.

A novel splicing mutation in the PKD1 gene causes autosomal dominant polycystic kidney disease in a Chinese family: a case report.

BACKGROUND: Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic renal disorder in humans, affecting 1 in 400 to 1000 individuals. Mutations PKD1 (which accounts for 85% of ADPKD and produces polycystin-1) and PKD2 (produces polycystin-2) are responsible for this disease. These two polycystins are critical for maintaining normal renal tubular structures during kidney development. CASE PRESENTATION: We performed genetic analysis on a family with ADPKD. DNA samples extracted from ADPKD patient blood were subject to targeted Next generation sequencing for human a panel of renal disease-related genes. A splicing mutation, c.2854-3C > G (also known as IVS11-3C > G), in the PKD1 gene was found in the 3 patients from the family, but was not found in four unaffected relatives and 100 normal control samples. Reverse transcription-PCR (RT-PCR) was performed to analyse the relative mRNA expression in the patient samples. mRNA sequencing showed that 29 bases inserted into the 3'-end of exon 11 in the PKD1 gene lead to a frameshift mutation. CONCLUSIONS: The PKD1 c.2854-3C > G mutation leads to a frameshift mutation during translation of the polycystin-1 protein, which eventually led to ADPKD in the Chinese family.

Genotype and phenotype correlations for SHANK3 de novo mutations in neurodevelopmental disorders.

SHANK3 has been identified as the causative gene of 22q13.3 microdeletion syndrome phenotype. De novo mutations (DNMs) of SHANK3 were subsequently identified in patients with several neurodevelopmental disorders, including autism spectrum disorders (ASDs), schizophrenia (SCZ), a Rett syndrome-like phenotype, and intellectual disability (ID). Although broad developmental phenotypes of these patients have been described in single studies, few studies have reviewed the genotype and phenotype relationships using a relatively large cohort of patients with SHANK3 DNMs. In this study, we identified a de novo splice mutation (NM_033517.1: c.2265+1G>A) that functionally impairs mRNA splicing, produces multiple splice variants, and results in the reduction of the amounts of mRNA. To analyze the genotype and phenotype correlations for SHANK3 DNMs, we reviewed 37 previously published patients with 28 SHANK3 DNMs. Our results revealed that haploinsufficiency of SHANK3 causes a broad spectrum of neurodevelopmental phenotypes with impaired social interaction, repetitive behavior, speech impairment, ID, and regression as the most common observations. Seizures, hypotonia, global development delay, dysmorphic features, and several other features also occurred recurrently. Specific phenotypes are also observed in certain genotypes. Our study provides the frequency of the heterogeneous co-occurring conditions caused by SHANK3 DNMs, which will be beneficial for diagnosis and clinical management.

FOXP3 mutations causing early-onset insulin-requiring diabetes but without other features of immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome.

Diabetes occurs in 1/90 000 to 1/160 000 births and when diagnosed under 6 months of age is very likely to have a primary genetic cause. FOXP3 encodes a transcription factor critical for T regulatory cell function and mutations are known to cause "immune dysregulation, polyendocrinopathy (including insulin-requiring diabetes), enteropathy, X-linked" (IPEX) syndrome. This condition is often fatal unless patients receive a bone-marrow transplant. Here we describe the phenotype of male neonates and infants who had insulin-requiring diabetes without other features of IPEX syndrome and were found to have mutations in FOXP3. Whole-exome or next generation sequencing of genes of interest was carried out in subjects with isolated neonatal diabetes without a known genetic cause. RT-PCR was carried out to investigate the effects on RNA splicing of a novel intronic splice-site variant. Four male subjects were found to have FOXP3 variants in the hemizygous state: p.Arg114Trp, p.Arg347His, p.Lys393Met, and c.1044+5G>A which was detected in 2 unrelated probands and in a brother diagnosed with diabetes at 2.1 years of age. Of these, p.Arg114Trp is likely a benign rare variant found in individuals of Ashkenazi Jewish ancestry and p.Arg347His has been previously described in patients with classic IPEX syndrome. The p.Lys393Met and c.1044+5G>A variants are novel to this study. RT-PCR studies of the c.1044+5G>A splice variant confirmed it affected RNA splicing by generating both a wild type and truncated transcript. We conclude that FOXP3 mutations can cause early-onset insulin-requiring diabetes with or without other features of IPEX syndrome.

Human ßA3/A1-crystallin splicing mutation causes cataracts by activating the unfolded protein response and inducing apoptosis in differentiating lens fiber cells.

ßγ-Crystallins, having a uniquely stable two domain four Greek key structure, are crucial for transparency of the eye lens,. Mutations in lens crystallins have been proposed to cause cataract formation by a variety of mechanisms most of which involve destabilization of the protein fold. The underlying molecular mechanism for autosomal dominant zonular cataracts with sutural opacities in an Indian family caused by a c.215+1G>A splice mutation in the ßA3/A1-crystallin gene CRYBA1 was elucidated using three transgenic mice models. This mutation causes a splice defect in which the mutant mRNA escapes nonsense mediated decay by skipping both exons 3 and 4. Skipping these exons results in an in-frame deletion of the mRNA and synthesis of an unstable p.Ile33_Ala119del mutant ßA3/A1-crystallin protein. Transgenic expression of mutant ßA3/A1-crystallin but not the wild type protein results in toxicity and abnormalities in the maturation and orientation of differentiating lens fibers in c.97_357del CRYBA1 transgenic mice, leading to a small spherical lens, cataract, and often lens capsule rupture. On a cellular level, the lenses accumulated p.Ile33_Ala119del ßA3/A1-crystallin with resultant activation of the stress signaling pathway - unfolded protein response (UPR) and inhibition of normal protein synthesis, culminating in apoptosis. This highlights the mechanistic contrast between mild mutations that destabilize crystallins and other proteins, resulting in their being bound by the α-crystallins that buffer lens cells against damage by denatured proteins, and severely misfolded proteins that are not bound by α-crystallin but accumulate and have a direct toxic effect on lens cells, resulting in early onset cataracts.

Analysis of 31-year-old patient with SYNGAP1 gene defect points to importance of variants in broader splice regions and reveals developmental trajectory of SYNGAP1-associated phenotype: case report.

BACKGROUND: Whole exome sequencing is a powerful tool for the analysis of genetically heterogeneous conditions. The prioritization of variants identified often focuses on nonsense, frameshift and canonical splice site mutations, and highly deleterious missense variants, although other defects can also play a role. The definition of the phenotype range and course of rare genetic conditions requires long-term clinical follow-up of patients. CASE PRESENTATION: We report an adult female patient with severe intellectual disability, severe speech delay, epilepsy, autistic features, aggressiveness, sleep problems, broad-based clumsy gait and constipation. Whole exome sequencing identified a de novo mutation in the SYNGAP1 gene. The variant was located in the broader splice donor region of intron 10 and replaced G by A at position +5 of the splice site. The variant was predicted in silico and shown experimentally to abolish the regular splice site and to activate a cryptic donor site within exon 10, causing frameshift and premature termination. The overall clinical picture of the patient corresponded well with the characteristic SYNGAP1-associated phenotype observed in previously reported patients. However, our patient was 31 years old which contrasted with most other published SYNGAP1 cases who were much younger. Our patient had a significant growth delay and microcephaly. Both features normalised later, although the head circumference stayed only slightly above the lower limit of the norm. The patient had a delayed puberty. Her cognitive and language performance remained at the level of a one-year-old child even in adulthood and showed a slow decline. Myopathic facial features and facial dysmorphism became more pronounced with age. Although the gait of the patient was unsteady in childhood, more severe gait problems developed in her teens. While the seizures remained well-controlled, her aggressive behaviour worsened with age and required extensive medication. CONCLUSIONS: The finding in our patient underscores the notion that the interpretation of variants identified using whole exome sequencing should focus not only on variants in the canonical splice dinucleotides GT and AG, but also on broader splice regions. The long-term clinical follow-up of our patient contributes to the knowledge of the developmental trajectory in individuals with SYNGAP1 gene defects.

Early-onset encephalopathy with epilepsy associated with a novel splice site mutation in SMC1A.

We report on the clinical and molecular characterization of a female patient with early-onset epileptic encephalopathy, who was found to carry a de novo novel splice site mutation in SMC1A. This girl shared some morphologic and anthropometric traits described in patients with clinical diagnosis of Cornelia de Lange syndrome and with SMC1A mutation but also has severe encephalopathy with early-onset epilepsy. In addition, she had midline hand stereotypies and scoliosis leading to the misdiagnosis of a Rett overlap syndrome. Molecular studies found a novel de novo splice site mutation (c.1911 + 1G > T) in SMC1A. This novel splice mutation was associated with an aberrantly processed mRNA that included intron 11 of the gene. Moreover, quantitative approach by RT-PCR showed a severe reduction of the SMC1A transcript suggesting that this aberrant transcript may be unstable and degraded. Taken together, our data suggest that the phenotype may be due to a loss-of-function of SMC1A in this patient. Our findings suggest that loss-of-function mutations of SMC1A may be associated with early-onset encephalopathy with epilepsy.

Congenital contractural arachnodactyly complicated with aortic dilatation and dissection: Case report and review of literature.

Congenital contractural arachnodactyly (CCA) is a connective tissue disease caused by mutations of the FBN2, which encodes fibrillin-2. CCA patients have a marfanoid habitus; however, aortic dilatation and/or dissection as observed in Marfan syndrome have been rarely documented. Here, we report on a Japanese familial case of CCA resulting from a FBN2 splicing mutation (IVS32+5g→a), which leads to exon 32 being skipped, and the patients developed aortic dilatation and type A dissection. Although CCA patients have been believed to have favorable prognoses, repetitive aortic imaging studies must be performed in some patients to detect possible aortic disease early, and genetic testing of FBN2 might be useful to identify such high-risk patients.

A novel NTRK1 splice site variant causing congenital insensitivity to pain with anhidrosis in a Chinese family.

Background: Congenital insensitivity to pain with anhidrosis (CIPA, OMIM #256800), also known as hereditary sensory and autonomic neuropathy type Ⅳ (HSAN-IV), is a rare autosomal recessive disorder characterized by recurrent episodic fevers, anhidrosis, insensitivity to noxious stimuli, self-mutilating behavior and intellectual disability. CIPA can be caused by the variants in NTRK1 gene, which encodes a high-affinity tyrosine kinase receptor for nerve growth factor. To ascertain the hereditary cause of a patient with CIPA accompanied by the additional symptoms of mild growth retardation, prone to fracture, underdeveloped nails of fingers and toes, irregular tooth alignment, enamel hypoplasia, postoperative wound healing difficulty, hand and limb deformity, and dislocation of hip joint, whole exome sequencing was used and revealed a compound heterozygous variant in NTRK1. Methods: DNA was extracted from peripheral blood samples of pediatric patients and their parents, and subjected to comprehensive analysis using whole-exome sequencing (WES), followed by verification of variant sites in the NTRK1 gene through Sanger sequencing. To elucidate the functional impact of the newly discovered variants, an in vitro experimental system was established. Splicing analysis was conducted using PCR and Sanger sequencing, while expression levels were assessed through qPCR and Western blot techniques. Results: One hotspot variant c.851-33T>A(ClinVar ID: 21308) and a novel variant c.850 + 5G>A(ClinVar ID:3069176) was inherited from her father and mother, respectively, identified in the affected individuals. The c.850 + 5G>A variant in NTRK1 resulted in two forms of aberrant mRNA splicing: 13bp deletion (c.838_850del13, p. Val280Ser fs180) and 25bp deletion (826_850del25, p. Val276Ser fs180) in exon 7, both leading to a translational termination at a premature stop codon and forming a C-terminal truncated protein. The expression of two abnormal splicing isoforms was decreased both in the level of mRNA and protein. Conclusion: In conclusion, this study elucidated the genetic cause of a patient with CIPA and identified a novel variant c.850 + 5G>A in NTRK1, which broadened the and enriched the NTRK1 mutation spectrum.

Case report: Analysis of a gene variant and prenatal diagnosis in a family with megalencephalic leukoencephalopathy with subcortical cysts.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare inherited cerebral white matter disorder in children. Pathogenic variations in the causative gene MLC1 are found in approximately 76% of patients and are inherited in an autosomal recessive manner. In this study, we identified an IVS2 + 1delG variant in MLC1 in the firstborn girl of a pregnant woman who has the clinical features of MLC, including macrocephaly, motor development delay, progressive functional deterioration, and myelinopathy, whereas no obvious subcortical cysts were observed by magnetic resonance imaging of the brain. The proband is homozygous for the IVS2 + 1delG mutation, which was inherited from the parents. This variant disrupts the donor splice site, causing an abnormal transcript that results in a premature termination codon and produces a truncated protein, which was confirmed to affect splicing by MLC1 cDNA analysis. This variant was also detected in family members, and a prenatal diagnosis for the fetus was undertaken. Eventually, the couple gave birth to an unaffected baby. Furthermore, we conducted a long-term follow-up of the proband's clinical course. This report improves our understanding of the genetic and phenotypic characteristics of MLC and provides a new genetic basis for prenatal diagnosis and genetic counseling.

Molecular and functional correction of a deep intronic splicing mutation in CFTR by CRISPR-Cas9 gene editing.

Cystic fibrosis (CF) is an autosomal recessive disorder caused by mutations in the CFTR gene. The 10th most common mutation, c.3178-2477C>T (3849+10kb C>T), involves a cryptic, intronic splice site. This mutation was corrected in CF primary cells homozygous for this mutation by delivering pairs of guide RNAs (gRNAs) with Cas9 protein in ribonucleoprotein (RNP) complexes that introduce double-strand breaks to flanking sites to excise the 3849+10kb C>T mutation, followed by DNA repair by the non-homologous end-joining pathway, which functions in all cells of the airway epithelium. RNP complexes were delivered to CF basal epithelial cell by a non-viral, receptor-targeted nanocomplex comprising a formulation of targeting peptides and lipids. Canonical CFTR mRNA splicing was, thus, restored leading to the restoration of CFTR protein expression with concomitant restoration of electrophysiological function in airway epithelial air-liquid interface cultures. Off-target editing was not detected by Sanger sequencing of in silico-selected genomic sites with the highest sequence similarities to the gRNAs, although more sensitive unbiased whole genome sequencing methods would be required for possible translational developments. This approach could potentially be used to correct aberrant splicing signals in several other CF mutations and other genetic disorders where deep-intronic mutations are pathogenic.

Functional and structural analysis of a novel splice site HMBS variant in a Chinese AIP patient.

Background: Acute intermittent porphyria (AIP) is a rare metabolic disorder that results from mutations in the gene encoding hydroxymethylbilane synthase (HMBS), an enzyme involved in heme biosynthesis. AIP follows an autosomal dominant inheritance pattern, but most carriers are asymptomatic. The clinical manifestations of AIP include acute attacks of abdominal pain and neuropsychiatric disturbances. The pathogenicity of novel HMBS variants identified in Chinese patients has not been well established. Objective: The article aims to identify the pathogenic mutation in an AIP patient and prove its pathogenicity through in vitro experiments. Methods: A 22-year-old female diagnosed with AIP participated in the study. Variant screening of her HMBS gene was carried out through Sanger sequencing. To ascertain the consequences of the newly discovered variant, we conducted in vitro experimentation targeting HMBS gene expression and enzymatic function. Additionally, protein structure analysis was performed. Cycloheximide treatment and UPF1-specific siRNA knockdown were employed to assess the impact of the mutation on the mechanism of non-sense-mediated mRNA decay (NMD). Results: A novel splice site variant in the HMBS gene (c.648_651+1delCCAGG) was detected in the patient, which caused aberrant mRNA splicing. In vitro experiments demonstrated that this variant significantly decreased the expression of HMBS. Further investigation confirmed that this decrease was due to NMD. Additionally, structural analysis indicated that this variant would destabilize the HMBS protein and impair its catalytic activity. To gain a comprehensive understanding of HMBS mutations in the context of AIP, we conducted a literature search on PubMed using the keywords 'HMBS' and 'Acute intermittent porphyria' from 2013 to 2023. This search yielded 19 clinical case reports written in English, which collectively described 220 HMBS gene mutations worldwide. Conclusion: The study identified and proved the pathogenicity of a novel splice site HMBS variant for the first time. Our results elucidated the pathological mechanism by which this mutation causes AIP through reducing HMBS expression and activity. These findings provide theoretical guidance for the diagnosis, treatment and genetic counseling of AIP patients.

RHD Genotypes in a Chinese Cohort of Pregnant Women.

RHD variants in D¯ Chinese pregnant women arose difficulties in management during pregnancy. Therefore, this study aims to precisely manage D¯ pregnant women by evaluating the spectrum of RHD mutations in D¯ pregnant women and getting insight into the possible rare alleles of RHD. A total of 76 D¯ pregnant women were analyzed by performing polymerase chain reactions with sequence-specific primers (PCR-SSP), the 10 RHD exons Sanger sequencing, RHD zygosity detection, and mRNA sequencing (mRNA-seq). About 40% of alleles are variations of RHD, including RHD 1227A homozygous, RHD-CE(2-9)-D, et al. Therefore, we developed a molecular diagnostic strategy for Chinese women, and most D¯ pregnant women can be diagnosed with this simple decision tree. After RHD genotyping for D¯ pregnancy women, we eliminated at least 15% unnecessary ante- and postpartum injections of Rh immunoglobulin (RhIG). As the first pedigree study and the first functional analysis under physiological conditions, mRNA-seq revealed that c.336-1G>A mutation mainly led to the inclusion of the intron 2, which indirectly explained the D¯ phenotype in this family. We also developed a robust protocol for determining fetal RhD status from maternal plasma. All 31 fetuses were predicted as RhD positive and confirmed the RhD status after birth.