Splice Site Mutation Research Articles

Novel MYBPC3 Mutations in Indian Population with Cardiomyopathies.

Mutations in Myosin Binding Protein C (MYBPC3) are one of the most frequent causes of cardiomyopathies in the world, but not much data are available in India. We carried out targeted direct sequencing of MYBPC3in 115 hypertrophic (HCM) and 127 dilated (DCM) cardiomyopathies against 197 ethnically matched healthy controls from India. We detected 34 single nucleotide variations in MYBPC3, of which 19 were novel. We found a splice site mutation [(IVS6+2T) T>G] and 16 missense mutations in Indian cardiomyopathies [5 in HCM; E258K, T262S, H287L, R408M, V483A: 4 in DCM; T146N, V321L, A392T, E393K and 7 in both HCM and DCM; L104M, V158M, S236G, R272C, T290A, G522E, A626V], but those were absent in 197 normal healthy controls. Interestingly, we found 7 out of 16 missense mutations (V158M, E258K, R272C, A392T, V483A, G522E, and A626V) in MYBPC3 were altering the evolutionarily conserved native amino acids, accounted for 8.7% and 6.3% in HCM and DCM, respectively. The bioinformatic tools predicted that those 7 missense mutations were pathogenic. Moreover, the co-segregation of those 7 mutations in families further confirmed their pathogenicity. Remarkably, we also identified compound mutations within the MYBPC3 gene of 6 cardiomyopathy patients (5%) with more severe disease phenotype; of which, 3 were HCM (2.6%) [(1. K244K + E258K + (IVS6+2T) T>G); (2. L104M + G522E + A626V); (3. P186P + G522E + A626V]; and 3 were DCM (2.4%) [(1. 5'UTR + A392T; 2. V158M+G522E; and 3.V158M + T262T + A626V]. The present comprehensive study on MYBPC3 has revealed both single and compound mutations in MYBPC3 and their association with disease in Indian Population with Cardiomyopathies. Our findings may perhaps help in initiating diagnostic strategies and eventually recognizing the targets for therapeutic interventions.

T-cell lymphoma patient harboring BCL11B mutations had favorable overall survival.

Molecular genetics serve a critical role in constructing risk stratification for hematological malignancies, but T-cell lymphoma (TCL) still lacks molecular genetic information for supplement risk stratification in predicting the prognosis of TCL patients. In the present study, we characterized the mutation patterns of B-cell leukemia/lymphoma 11B gene (BCL11B) and its prognostic importance in TCL patients. BCL11B mutations were characterized based on the data from two datasets, one is from our clinical center (GDPH dataset, n=79) and the other is from COSMIC dataset (n=154). The overall mutation rate of BCL11B was 6.4% (15/233) in TCL, and there were no hotspot mutation sites in TCL. Among these mutations, the missense and splice site mutation were significantly prominent. Moreover, TCL patients harboring BCL11B mutations had a favorable overall survival (OS) in our center (GDPH dataset) (adjusted hazard ratio [HR]=.001, p=0.109), although there were not yet significantly statistical at this point. In addition, TCL patients harboring BCL11B mutation had a longer 5-year restricted mean survival time (RMST) than those without a BCL11B mutation (60vs. 32 months). Notably, BCL11B mutations were not associated with TCL entities having better prognosis. BCL11B mutations were associated with favorable clinical outcome for TCL patients; it might be considered as a novel biomarker for TCL prognostic stratification.

Partial penetrance and phenotypic variability of aplasia of lacrimal and salivary glands caused by a novel FGF10 donor splice-site mutation.

Thirteen affected individuals of six generations of a single kindred presented with epiphora evident from infancy. Physical exam and Schirmer test revealed variable expression of tear deficiency, congenital punctal atresia, and dry mouth with multiple caries, without concomitant abnormalities of the ears or digits, commensurate with a diagnosis of aplasia of the lacrimal and salivary glands (ALSG). Reconstruction of the upper lacrimal drainage system was performed in some of the affected individuals. Genetic analysis, testing six affected individuals and three non-affected family members, identified a single novel heterozygous splice-site variant, c.429 + 1, G > T in fibroblast growth factor 10 (FGF10) (NM_004465.1), segregating throughout the family as expected for dominant heredity. RT-PCR assays of HEK-293 cells transfected with wild type or mutant FGF10 demonstrated that the variant causes skipping of Exon 2. Notably, individuals sharing the same variant exhibited phenotypic variability, with unilateral or bilateral epiphora, as well as variable expression of dry mouth and caries. Moreover, one of the variant carriers had no ALSG-related clinical findings, demonstrating incomplete penetrance. While coding mutations in FGF10 are known to cause malformations in the nasolacrimal system, this is the second FGF10 splice-site variant and the first donor-site variant reported to cause ALSG. Thus, our study of a unique large kindred with multiple affected individuals heterozygous for the same FGF10 variant highlights intronic splice-site mutations and phenotypic variability/partial penetrance in ALSG.

Relevance of ATM Status in Driving Sensitivity to DNA Damage Response Inhibitors in Patient-Derived Xenograft Models.

Ataxia-telangiectasia mutated gene (ATM) is a key component of the DNA damage response (DDR) and double-strand break repair pathway. The functional loss of ATM (ATM deficiency) is hypothesised to enhance sensitivity to DDR inhibitors (DDRi). Whole-exome sequencing (WES), immunohistochemistry (IHC), and Western blotting (WB) were used to characterise the baseline ATM status across a panel of ATM mutated patient-derived xenograft (PDX) models from a range of tumour types. Antitumour efficacy was assessed with poly(ADP-ribose)polymerase (PARP, olaparib), ataxia- telangiectasia and rad3-related protein (ATR, AZD6738), and DNA-dependent protein kinase (DNA-PK, AZD7648) inhibitors as a monotherapy or in combination to associate responses with ATM status. Biallelic truncation/frameshift ATM mutations were linked to ATM protein loss while monoallelic or missense mutations, including the clinically relevant recurrent R3008H mutation, did not confer ATM protein loss by IHC. DDRi agents showed a mixed response across the PDX's but with a general trend toward greater activity, particularly in combination in models with biallelic ATM mutation and protein loss. A PDX with an ATM splice-site mutation, 2127T > C, with a high relative baseline ATM expression and KAP1 phosphorylation responded to all DDRi treatments. These data highlight the heterogeneity and complexity in describing targetable ATM-deficiencies and the fact that current patient selection biomarker methods remain imperfect; although, complete ATM loss was best able to enrich for DDRi sensitivity.

Inactivating TDP2 missense mutation in siblings with congenital abnormalities reminiscent of fanconi anemia

Mutations in TDP2, encoding tyrosyl-DNA phosphodiesterase 2, have been associated with a syndromal form of autosomal recessive spinocerebellar ataxia, type 23 (SCAR23). This is a very rare and progressive neurodegenerative disorder described in only nine patients to date, and caused by splice site or nonsense mutations that result in greatly reduced or absent TDP2 protein. TDP2 is required for the rapid repair of DNA double-strand breaks induced by abortive DNA topoisomerase II (TOP2) activity, important for genetic stability in post-mitotic cells such as neurons. Here, we describe a sibship that is homozygous for the first TDP2 missense mutation (p.Glu152Lys) and which presents with clinical features overlapping both SCAR23 and Fanconi anemia (FA). We show that in contrast to previously reported SCAR23 patients, fibroblasts derived from the current patient retain significant levels of TDP2 protein. However, this protein is catalytically inactive, resulting in reduced rates of repair of TOP2-induced DNA double-strand breaks and cellular hypersensitivity to the TOP2 poison, etoposide. The TDP2-mutated patient-derived fibroblasts do not display increased chromosome breakage following treatment with DNA crosslinking agents, but both TDP2-mutated and FA cells exhibit increased chromosome breakage in response to etoposide. This suggests that the FA pathway is required in response to TOP2-induced DNA lesions, providing a possible explanation for the clinical overlap between FA and the current TDP2-mutated patients. When reviewing the relatively small number of patients with SCAR23 that have been reported, it is clear that the phenotype of such patients can extend beyond neurological features, indicating that the TDP2 protein influences not only neural homeostasis but also other tissues as well.

Mutations in DARS2 result in global dysregulation of mRNA metabolism and splicing

Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is a rare neurological disorder caused by the mutations in the DARS2 gene, which encodes the mitochondrial aspartyl-tRNA synthetase. The objective of this study was to understand the impact of DARS2 mutations on cell processes through evaluation of LBSL patient stem cell derived cerebral organoids and neurons. We generated human cerebral organoids (hCOs) from induced pluripotent stem cells (iPSCs) of seven LBSL patients and three healthy controls using an unguided protocol. Single cells from 70-day-old hCOs were subjected to SMART-seq2 sequencing and bioinformatic analysis to acquire high-resolution gene and transcript expression datasets. Global gene expression analysis demonstrated dysregulation of a number of genes involved in mRNA metabolism and splicing processes within LBSL hCOs. Importantly, there were distinct and divergent gene expression profiles based on the nature of the DARS2 mutation. At the transcript level, pervasive differential transcript usage and differential spliced exon events that are involved in protein translation and metabolism were identified in LBSL hCOs. Single-cell analysis of DARS2 (exon 3) showed that some LBSL cells exclusively express transcripts lacking exon 3, indicating that not all LBSL cells can benefit from the “leaky” nature common to splice site mutations. At the gene- and transcript-level, we uncovered that dysregulated RNA splicing, protein translation and metabolism may underlie at least some of the pathophysiological mechanisms in LBSL. To confirm hCO findings, iPSC-derived neurons (iNs) were generated by overexpressing Neurogenin 2 using lentiviral vector to study neuronal growth, splicing of DARS2 exon 3 and DARS2 protein expression. Live cell imaging revealed neuronal growth defects of LBSL iNs, which was consistent with the finding of downregulated expression of genes related to neuronal differentiation in LBSL hCOs. DARS2 protein was downregulated in iNs compared to iPSCs, caused by increased exclusion of exon 3. The scope and complexity of our data imply that DARS2 is potentially involved in transcription regulation beyond its canonical role of aminoacylation. Nevertheless, our work highlights transcript-level dysregulation as a critical, and relatively unexplored, mechanism linking genetic data with neurodegenerative disorders.

Hypoparathyroidism, deafness and renal dysplasia syndrome caused by a GATA3 splice site mutation leading to the activation of a cryptic splice site.

The HDR syndrome is a rare autosomal dominant disorder characterised by Hypoparathyroidism, Deafness, and Renal dysplasia, and is caused by inactivating heterozygous germline mutations in the GATA3 gene. We report an 11-year-old girl with HDR syndrome caused by a heterozygous mutation located at the splice acceptor site of exon 5 of the GATA3 gene (NM_001002295.2: c.925-1G>T). Functional studies using a minigene assay showed that this splice site mutation abolished the normal splicing of the GATA3 pre-mRNA and led to the use of a cryptic splice acceptor site, resulting in the loss of the first seven nucleotides (TCTGCAG) of exon 5 in the GATA3 mRNA. These findings increase the understanding of the mechanisms by which GATA3 splicing mutations can cause HDR syndrome.

Immunologic and Genetic Contributors to CD46-Dependent Immune Dysregulation

Mutations in CD46 predispose to atypical hemolytic uremic syndrome (aHUS) with low penetrance. Factors driving immune-dysregulatory disease in individual mutation carriers have remained ill-understood. In addition to its role as a negative regulator of the complement system, CD46 modifies T cell-intrinsic metabolic adaptation and cytokine production. Comparative immunologic analysis of diseased vs. healthy CD46 mutation carriers has not been performed in detail yet. In this study, we comprehensively analyzed clinical, molecular, immune-phenotypic, cytokine secretion, immune-metabolic, and genetic profiles in healthy vs. diseased individuals carrying a rare, heterozygous CD46 mutation identified within a large single family. Five out of six studied individuals carried a CD46 gene splice-site mutation causing an in-frame deletion of 21 base pairs. One child suffered from aHUS and his paternal uncle manifested with adult-onset systemic lupus erythematosus (SLE). Three mutation carriers had no clinical evidence of CD46-related disease to date. CD4+ T cell-intrinsic CD46 expression was uniformly 50%-reduced but was comparable in diseased vs. healthy mutation carriers. Reconstitution experiments defined the 21-base pair-deleted CD46 variant as intracellularly—but not surface-expressed and haploinsufficient. Both healthy and diseased mutation carriers displayed reduced CD46-dependent T cell mitochondrial adaptation. Diseased mutation carriers had lower peripheral regulatory T cell (Treg) frequencies and carried potentially epistatic, private rare variants in other inborn errors of immunity (IEI)-associated proinflammatory genes, not found in healthy mutation carriers. In conclusion, low Treg and rare non-CD46 immune-gene variants may contribute to clinically manifest CD46 haploinsufficiency-associated immune-dysregulation.

Best-corrected visual acuity results facilitate molecular diagnosis of infantile nystagmus patients harboring FRMD7 mutations

The visual function of patients with infantile nystagmus (IN) can be significantly decreased owing to constant eye movement. While, reaching a definitive diagnosis becomes a challenge due to genetic heterozygous of this disease. To address it, we investigated whether best-corrected visual acuity (BCVA) results can facilitate the molecular diagnosis of IN patients harboring FRMD7 mutations. 200 patients with IN from 55 families and 133 sporadic cases were enrolled. Mutations were comprehensively screened by direct sequencing using gene-specific primers for FRMD7. We also retrieved related literature to verify the results based on our data. We found that the BCVA of patients with IN harboring FRMD7 mutations was between 0.5 and 0.7, which was confirmed by data retrieved from the literature. Our results showed that BCVA results facilitate the molecular diagnosis of patients with IN harboring FRMD7 mutations. In addition, we identified 31 FRMD7 mutations from the patients, including six novel mutations, namely, frameshift mutation c.1492_1493insT (p.Y498LfsTer14), splice-site mutation c.353C > G, three missense mutations [c.208C > G (p.P70A), c.234G > A (p.M78I), and c.1109G > A (p.H370R)], and nonsense mutation c.1195G > T (p.E399Ter). This study demonstrates that BCVA results may facilitate the molecular diagnosis of IN patients harboring FRMD7 mutations.

Identification of five novel variants of ADAR1 in dyschromatosis symmetrica hereditaria by next-generation sequencing.

Dyschromatosis symmetrica hereditaria (DSH) is a rare autosomal dominant inherited pigmentary dermatosis characterized by a mixture of hyperpigmented and hypopigmented freckles on the dorsal aspect of the distal extremities. To date, pathogenic mutations causing DSH have been identified in the adenosine deaminase acting on RNA1 gene (ADAR1), which is mapped to chromosome 1q21. The present study aimed to investigate the underlying pathological mechanism in 14 patients with DSH from five unrelated Chinese families. Next-generation sequencing (NGS) and direct sequencing were performed on a proband with DSH to identify causative mutations. All coding, adjacent intronic, and 5'- and 3'-untranslated regions of ADAR1 were screened, and variants were identified. These mutations consisted of three missense mutations (NM_001025107: c.716G>A, NM_001111.5: c.3384G>C, and NM_001111.5: c.3385T>G), one nonsense mutation (NM_001111.5:c.511G>T), and one splice-site mutation (NM_001111.5: c.2080-1G>T) located in exon 2, exon 14, and the adjacent intronic region according to recommended Human Genome Variation Society (HGVS) nomenclature. Moreover, using polymerase chain reaction and Sanger sequencing, we identified five novel ADAR1 variants, which can be predicted to be pathogenic by in silico genome sequence analysis. Among the mutations, the missense mutations had no significant effect on the spatial structure of the protein, while the stop codon introduced by the nonsense mutation truncated the protein. Our results highlighted that the advent of NGS has facilitated high-throughput screening for the identification of disease-causing mutations with high accuracy, stability, and specificity. Five novel genetic mutations were found in five unrelated families, thereby extending the pathogenic mutational spectrum of ADAR1 in DSH and providing new insights into this complex genetic disorder.

Screening for PRX mutations in a large Chinese Charcot-Marie-Tooth disease cohort and literature review.

Periaxins (encoded by PRX) play an important role in the stabilization of peripheral nerve myelin. Mutations in PRX can lead to Charcot-Marie-Tooth disease type 4F (CMT4F). In this study, we screened for PRX mutations using next-generation sequencing and whole-exome sequencing in a large Chinese CMT cohort consisting of 465 unrelated index patients and 650 healthy controls. Sanger sequencing was used for the validation of all identified variants. We also reviewed all previously reported PRX-related CMT cases and summarized the clinical manifestations and genetic features of PRX-related CMTs. The hit rate for biallelic PRX variants in our cohort of Chinese CMT patients was 0.43% (2/465). One patient carried a previously unreported splice-site mutation (c.25_27 + 9del) compound heterozygous with a known nonsense variant. Compiling data on CMT4F cases and PRX variants from the medical literature confirmed that early-onset (95.2%), distal amyotrophy or weakness (94.0%), feet deformity (75.0%), sensory impairment or sensory ataxia (65.5%), delayed motor milestones (60.7%), and spinal deformity (59.5%) are typical features for CMT4F. Less frequent features were auditory impairments, respiratory symptoms, late onset, dysarthria or hoarseness, ophthalmic problems, and central nervous system involvement. The two cases with biallelic missense mutations have later onset age than those with nonsense or frameshift mutations. We did not note clear correlations between the type and site of mutations and clinical severity or distinct constellations of symptoms. Consistent with observations in other countries and ethnic groups, PRX-related CMT is rare in China. The clinical spectrum is wider than previously anticipated.

A single F153Sβ3 mutation causes constitutive integrin αIIbβ3 activation in a variant form of Glanzmann thrombasthenia.

This report identifies a novel variant form of the inherited bleeding disorder Glanzmann thrombasthenia, exhibiting only mild bleeding in a physically active individual. The platelets cannot aggregate exvivo with physiologic agonists of activation, although microfluidic analysis with whole blood displays moderate exvivo platelet adhesion and aggregation consistent with mild bleeding. Immunocytometry shows reduced expression of αIIbβ3 on quiescent platelets that spontaneously bind/store fibrinogen, and activation-dependent antibodies (ligand-induced binding site-319.4 and PAC-1) report β3 extension suggesting an intrinsic activation phenotype. Genetic analysis reveals a single F153Sβ3 substitution within the βI-domain from a heterozygous T556C nucleotide substitution of ITGB3 exon 4 in conjunction with a previously reported IVS5(+1)G>A splice site mutation with undetectable platelet messenger RNA accounting for hemizygous expression of S153β3. F153 is completely conserved among β3 of several species and all human β-integrin subunits suggesting that it may play a vital role in integrin structure/function. Mutagenesis of αIIb-F153Sβ3 also displays reduced levels of a constitutively activated αIIb-S153β3 on HEK293T cells. The overall structural analysis suggests that a bulky aromatic, nonpolar amino acid (F,W)153β3 is critical for maintaining the resting conformation of α2- and α1-helices of the βI-domain because small amino acid substitutions (S,A) facilitate an unhindered inward movement of the α2- and α1-helices of the βI-domain toward the constitutively active αIIbβ3 conformation, while a bulky aromatic, polar amino acid (Y) hinders such movements and restrains αIIbβ3 activation. The data collectively demonstrate that disruption of F153β3 can significantly alter normal integrin/platelet function, although reduced expression of αIIb-S153β3 may be compensated by a hyperactive conformation that promotes viable hemostasis.

BG05 Artificial intelligence prediction of splice site mutation consequences in junctional epidermolysis bullosa: signposts to severity

Abstract Over one-fifth of disease-causing mutations in junctional epidermolysis bullosa (JEB) are splice site variants. These affect pre-mRNA splicing through the activation of cryptic splice sites and/or exon skipping, resulting in altered mRNA and translated proteins. Prediction of the precise location of activated cryptic splice sites is vital, as these can potentially alter the reading frame of the resulting transcript. Out-of-frame transcripts contain premature termination complexes (PTCs), which generally result in nonfunctional protein and often correlate with severe JEB in conjunction with other PTC-introducing mutations. SpliceAI is a 32-layer convolutional neural network that examines 10 000 nucleotides of flanking sequence around a variant of interest to predict its effects on RNA splicing. It was used to predict splice site mutation consequences in five patients with JEB with LAMB3 mutations. Genotypes, predicted transcripts and JEB subtypes are summarized in Table 1. SpliceAI predicted PTCs in cases 1 and 2, where transcripts were either out of frame or novel PTCs were introduced following aberrant splicing. An in-frame transcript with no PTC was predicted for case 3, which may explain this individual’s mild phenotype. Reverse transcriptase polymerase chain reaction data were reviewed for cases 4 and 5, and two predicted transcripts were confirmed. Two additional in-frame transcripts not predicted by SpliceAI were found to be produced in low levels. It is likely that these in-frame transcripts generated partially functional protein, alleviating JEB severity to a degree. This study highlights the importance of examining RNA transcripts for accurate genotype–phenotype correlation. In silico tools such as SpliceAI show potential in elucidating mechanisms of severity. They may facilitate selection of cases for further laboratory investigation and can guide which regions of the gene or transcript to sequence for confirmatory analyses. Where RNA analyses were available, SpliceAI correctly predicted two of the resultant transcripts. Further validation of this tool is required with additional cases in this rare disease.Table 1Genotypes, predicted transcripts and JEB subtypes found with SpliceAICaseZygosityMutation (LAMB3)Exon skipping predictionCryptic splice site activation predictionPredicted outcome commentsJEB subtype1Homozygousc.2701+1G>AOOF exon 18 skipping20 nt excluded from exon 18Both outcomes OOFSevere2Heterozygousc.565-2A>G, c.2914C>T (p.R972X)OOF exon 7 skipping117 nt included from intron 6 (including TGA PTC at c.565-60)In-frame cryptic activation with novel PTC introducedSevereOOF exon skipping3Heterozygousc.1705C>T (p.R569X), c.943+2T>COOF exon 9 skipping27 nt included from intron 9In-frame cryptic activationIntermediateOOF exon skipping4Homozygousc.298+5G>COOF exon 4 skipping64 nt included from intron 4Both outcomes OOFIntermediate5Heterozygousc.3119G>A (p.W1040X), c.629-12T>APredicted to be unlikely10 nt included from intron 7OOF cryptic activationIntermediatent, nucleotides; OOF, out of frame.

In Silico Analysis to Predict the Pathogenic Variants of CANT1 Gene Causing Desbuquios Dysplasia (DBQD) Type 1

Desbuquois dysplasia (DBQD) is an autosomal recessive chondrodysplasia that belongs to the multiple dislocation group and causes parental and afterbirth growth retardation, hand and proximal femur abnormalities, joint laxity, and scoliosis. Several missense and splice site mutations in CANT1 gene are linked with the development of DBQD. In silico approaches can predict the pathogenic variations causing hereditary diseases. Hence, in the current study, in silico analysis was used to forecast the variants of CANT1 gene that harm the functionality of calcium-dependent nucleotidase. A total of 281 variants with uncertain significance, retrieved from the gnomAD, dbSNP, ClinVar, and Variation Viewer databases, were analyzed using CADD, Meta SNP, CAPiCE, and Condel to predict 61 highly pathogenic variants. Stability change predicting computational tools were applied to filter 19 highly pathogenic amino acid variants that impact protein dynamics via sample conformation or during vibrational entropy. UCSF Chimera was used for interactive visualization and analysis of unwanted interaction among 5 variants in the molecular structure of the protein. Ligand binding computational tools were used to interpret the protein-ligand interactions. A total of three (3) post-translational modification sites were also predictably disrupted by 16 variants. Spice and HSF 3.1 tools were applied to 95 variants to check their disease-causing potential. The variants of the gene were analyzed using computational tools based on different algorithms. The most damaging variants of CANT1 gene that can affect the functionality and stability of the protein were predicted. It was determined that an extensive in silico analysis can determine the likely pathogenic variations for further in vitro experimental analysis.

IFT74 variants cause skeletal ciliopathy and motile cilia defects in mice and humans.

Motile and non-motile cilia play critical roles in mammalian development and health. These organelles are composed of a 1000 or more unique proteins, but their assembly depends entirely on proteins synthesized in the cell body and transported into the cilium by intraflagellar transport (IFT). In mammals, malfunction of non-motile cilia due to IFT dysfunction results in complex developmental phenotypes that affect most organs. In contrast, disruption of motile cilia function causes subfertility, disruption of the left-right body axis, and recurrent airway infections with progressive lung damage. In this work, we characterize allele specific phenotypes resulting from IFT74 dysfunction in human and mice. We identified two families carrying a deletion encompassing IFT74 exon 2, the first coding exon, resulting in a protein lacking the first 40 amino acids and two individuals carrying biallelic splice site mutations. Homozygous exon 2 deletion cases presented a ciliary chondrodysplasia with narrow thorax and progressive growth retardation along with a mucociliary clearance disorder phenotype with severely shorted cilia. Splice site variants resulted in a lethal skeletal chondrodysplasia phenotype. In mice, removal of the first 40 amino acids likewise results in a motile cilia phenotype but with little effect on primary cilia structure. Mice carrying this allele are born alive but are growth restricted and developed hydrocephaly in the first month of life. In contrast, a strong, likely null, allele of Ift74 in mouse completely blocks ciliary assembly and causes severe heart defects and midgestational lethality. In vitro studies suggest that the first 40 amino acids of IFT74 are dispensable for binding of other IFT subunits but are important for tubulin binding. Higher demands on tubulin transport in motile cilia compared to primary cilia resulting from increased mechanical stress and repair needs could account for the motile cilia phenotype observed in human and mice.

The mutational landscape of Chinese breast cancer by liquid biopsy.

e13117 Background: Breast cancer is the most common malignancy worldwide. The novel technique of liquid biopsy provides further prospect of breast cancer management. However, the clinical application of liquid biopsy for breast cancer remains clearly defined. Methods: Blood samples of 145 Chinese patients diagnosed as breast cancer were collected. cfDNA were analyzed by next-generation sequencing technique using Haplox HapOnco panel. The mutations of cfDNA were analyzed and compared with genomic mutations detected within tumor tissues of breast cancer patients. Results: In total, 327 genetic mutations were detected in 145 patients using cfDNA. The top 5 high frequent alterations were TP53(50.3%), PIK3CA (42.8%), SYNE1 (16.6%), ESR1 (10.3%), CSMD3 (9.0%). Within TP53 mutations, 13.7% were frame shift insertions or deletions, 5.5% were in-frame insertions or deletions, 9.6% were splice site mutations. Within PIK3CA mutations, 1.6% were in-frame insertions or deletions, 1.6% were copy number variations. The average number of mutations for each patient was 7.2 (5.5 to 9.0, 95% CI). The mutated genes in cfDNA were compared with those in tumor tissues in publications. 208 mutated genes in tumor tissues were also detected in cfDNA. There was no significant difference in mutation rate for 83.6% genes in blood and tumor tissues. Conclusions: Most mutated genes in tumor tissues of breast cancer patients could be detected in cfDNA. The mutation rate for most genes had no significant difference in blood and tumor tissues, which indicated that liquid biopsy using cfDNA is a promising technique to improve breast cancer management.

Adult‐onset leukoencephalopathy with axonal spheroids and pigmented glia caused by a novel mutation of CSF1R gene

AbstractBackgroundAdult‐onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) is a rare autosomal dominant disorder caused by mutations in the colony‐stimulating factor 1 receptor (CSF1R) gene. As of 2022, more than 100 different CSF1R mutations were reported in patients with CSF1R‐related leukoencephalopathy.MethodIn this case report, we described ALSP in a previously healthy 46‐year‐old woman. The patient underwent detailed neurological examinations including cognitive assessment, brain magnetic resonance imaging (MRI) and whole‐exome sequencing.ResultThe patient manifested as memory impairment, poor interpersonal behavior and decreased verbal fluency. Brain MRI showed confluent white matter changes and atrophy of the corpus callosum. Whole‐exome sequencing identified a novel splice site mutation (C.1858 + 5G > A) in intron 13 of the CSF1R gene, which has not been reported worldwide.ConclusionALSP has a wide range of clinical manifestations and genetic heterogeneity. It should be considered when diagnosing rapidly progressive dementia with or without motor impairment. We recommend biopsy or genetic testing in these patients to avoid misdiagnosis and delayed diagnosis. We will continue to monitor this family in the future to improve our understanding of ALSP, so as to correctly diagnose ALSP in clinic and provide clinical data for better research on the pathogenesis and treatment of this disease.

Two Novel and a Recurrent ATP2C1 Mutations in Chinese Population with Hailey-Hailey Disease.

Hailey-Hailey disease (HHD), also known as familial benign chronic pemphigus, is a rare autosomal dominant inherited blistering dermatosis. Pathogenic variants in ATP2C1 have been associated with HHD since 2000. This study aimed to identify the mutations in the ATP2C1 gene in two Chinese pedigrees and two sporadic cases with HHD. Two Chinese pedigrees and two sporadic cases were included in this study. Whole-exome sequencing and Sanger sequencing were performed to detect the mutation of the ATP2C1 gene. Predictions of protein structure and function were performed using bioinformatics tools, including Mutation Taster, Polyphen-2, SIFT, and Swiss-Model. In this study, we detected three heterozygous mutations, including novel compound mutations of (c.1840-4delA and c.1840_1844delGTTGC), splice site mutation of c.1570+3A>C, and a previously known nonsense mutation c.1402C>T in the ATP2C1 gene. Combined with our previous study, ten patients with c.1402C>T mutation in the ATP2C1 gene have been identified, and all these patients originated from Jiangxi Province. c.1402C>T mutation in the ATP2C1 gene was considered a regional highly prevalent mutation in the Chinese population with HHD. The results added new variants to the database of ATP2C1 mutations associated with HHD.

Exceptional Response to Bromodomain and Extraterminal Domain Inhibitor Therapy With BMS-986158 in BRD4-NUTM1 NUT Carcinoma Harboring a BRD4 Splice Site Mutation.

Exceptional Response to Bromodomain and Extraterminal Domain Inhibitor Therapy With BMS-986158 in BRD4-NUTM1 NUT Carcinoma Harboring a BRD4 Splice Site Mutation.

FAM20A mutations and transcriptome analyses of dental pulp tissues of enamel renal syndrome.

Biallelic loss-of-function FAM20A mutations cause amelogenesis imperfecta (AI) type IG, better known as enamel renal syndrome (ERS), characterized by severe enamel hypoplasia, delayed/failed tooth eruption, intrapulpal calcifications, gingival hyperplasia and nephrocalcinosis. FAM20A binds to FAM20C, the Golgi casein kinase (GCK) and potentiates its function to phosphorylate secreted proteins critical for biomineralization. While many FAM20A pathogenic mutations have been reported, the pathogeneses of orodental anomalies in ERS remain to be elucidated. This study aimed to identify disease-causing mutations for patients with ERS phenotypes and to discern the molecular mechanism underlying ERS intrapulpal calcifications. Phenotypic characterization and whole exome analyses were conducted for 8 families and 2 sporadic cases with hypoplastic AI. A minigene assay was performed to investigate the molecular consequences of a FAM20A splice-site variant. RNA sequencing followed by transcription profiling and gene ontology (GO) analyses were carried out for dental pulp tissues of ERS and the control. Biallelic FAM20A mutations were demonstrated for each affected individual, including 7 novel pathogenic variants: c.590-5T>A, c.625T>A (p.Cys209Ser), c.771del (p.Gln258Argfs*28), c.832_835delinsTGTCCGACGGTGTCCGACGGTGTC CA (p.Val278Cysfs*29), c.1232G>A (p.Arg411Gln), c.1297A>G (p.Arg433Gly) and c.1351del (p.Gln451Serfs*4). The c.590-5T>A splice-site mutation caused Exon 3 skipping, which resulted in an in-frame deletion of a unique region of the FAM20A protein, p.(Asp197_Ile214delinsVal). Analyses of differentially expressed genes in ERS pulp tissues demonstrated that genes involved in biomineralization, particularly dentinogenesis, were significantly upregulated, such as DSPP, MMP9, MMP20 and WNT10A. Enrichment analyses indicated overrepresentation of gene sets associated with BMP and SMAD signalling pathways. In contrast, GO terms related to inflammation and axon development were underrepresented. Among BMP signalling genes, BMP agonists GDF7, GDF15, BMP3, BMP8A, BMP8B, BMP4 and BMP6 were upregulated, while BMP antagonists GREM1, BMPER and VWC2 showed decreased expression in ERS dental pulp tissues. Upregulation of BMP signalling underlies intrapulpal calcifications in ERS. FAM20A plays an essential role in pulp tissue homeostasis and prevention of ectopic mineralization in soft tissues. This critical function probably depends upon MGP (matrix Gla protein), a potent mineralization inhibitor that must be properly phosphorylated by FAM20A-FAM20C kinase complex.