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Summary: Juvenile myelomonocytic leukaemia (JMML) is an aggressive paediatric leukaemia characterized by mutations in five canonical RAS pathway genes, including the NF1 gene. JMML is driven by germline NF1 gene mutations, with additional somatic aberrations resulting in the NF1 biallelic inactivation, leading to disease progression. Germline mutations in the NF1 gene alone primarily cause benign neurofibromatosis type 1 (NF1) tumours rather than malignant JMML, yet the underlying mechanism remains unclear. Here, we demonstrate that with reduced NF1 gene dose, immune cells are promoted in anti‐tumour immune response. Comparing the biological properties of JMML and NF1 patients, we found that not only JMML but also NF1 patients driven by NF1 mutations could increase monocytes generation. But monocytes cannot further malignant development in NF1 patients. Utilizing haematopoietic and macrophage differentiation from iPSCs, we revealed that NF1 mutations or knockout (KO) recapitulated the classical haematopoietic pathological features of JMML with reduced NF1 gene dose. NF1 mutations or KO promoted the proliferation and immune function of NK cells and iMacs derived from iPSCs. Moreover, NF1‐mutated iNKs had a high capacity to kill NF1‐KO iMacs. NF1‐mutated or KO iNKs administration delayed leukaemia progression in a xenograft animal model. Our findings demonstrate that germline NF1 mutations alone cannot directly drive JMML development and suggest a potential cell immunotherapy for JMML patients. [ABSTRACT FROM AUTHOR]

Background: Tricho‐rhino‐phalangeal syndrome (TRPS) is a rare autosomal dominant disorder characterized by craniofacial and skeletal malformations including short stature, thin scalp hair, sparse lateral eyebrows, a pear‐shaped nose, and cone‐shaped epiphyses. This condition is caused by haploinsufficiency or dominant‐negative effect of the TRPS1 gene. Methods: In this study, we analyzed the clinical and genetic data of five unrelated TRPS patients. They were suspected of having TRPS on the basis of clinical and radiological features including typical hair and facial features, as well as varying degrees of skeletal abnormalities. Next‐generation sequencing was performed to identify variants of the TRPS1 gene in the five patients. Results: In patient 1, we found a novel mutation at c.1338C>A (p.Tyr446*) (de novo). Patient 2 had a novel phenotype of hydrocephaly and Arnold–Chiari syndrome and we also found a maternally inherited novel mutation at c.2657C>A (p.Ser886*). Patient 3 had a de novo novel mutation at c.2726G>C (p.Cys909Ser) leading to more severe phenotypes. Patient 4 had a paternally inherited known mutation at c.2762G>A (p.Arg921Gln). Patient 5 with a novel phenotype of hepatopathy had a novel deletion at [GRCh37] del(8)(q23.3‐q24.11) chr8:g.116,420,724‐119,124,058 (over 2,700 kb). In addition, the patient 3 who harboring missense variants in the GATA binding domain of TRPS1 showed more severe craniofacial and skeletal phenotypes. Conclusions: We describe four novel mutations and two novel phenotypes in five patients. The mutational and phenotypic spectrum of TRPS is broadened by our study on TRPS mutations. Our results reveal the significance of molecular analysis of TRPS1 for improving the clinical diagnosis of TRPS. [ABSTRACT FROM AUTHOR]

Noonan syndrome (NS) is a common autosomal dominant/recessive disorder. No large‐scale study has been conducted on NS in China, which is the most populous country in the world. Next‐generation sequencing (NGS) was used to identify pathogenic variants in patients that exhibited NS‐related phenotypes. We assessed the facial features and clinical manifestations of patients with pathogenic or likely pathogenic variants in the RAS‐MAPK signaling pathway. Gene‐related Chinese NS facial features were described using artificial intelligence (AI).NGS identified pathogenic variants in 103 Chinese patients in eight NS‐related genes: PTPN11 (48.5%), SOS1 (12.6%), SHOC2 (11.7%), KRAS (9.71%), RAF1 (7.77%), RIT1 (6.8%), CBL (0.97%), NRAS (0.97%), and LZTR1 (0.97%). Gene‐related facial representations showed that each gene was associated with different facial details. Eight novel pathogenic variants were detected and clinical features because of specific genetic variants were reported, including hearing loss, cancer risk due to a PTPN11 pathogenic variant, and ubiquitous abnormal intracranial structure due to SHOC2 pathogenic variants. NGS facilitates the diagnosis of NS, especially for patients with mild/moderate and atypical symptoms. Our study describes the genotypic and phenotypic spectra of NS in China, providing new insights into distinctive clinical features due to specific pathogenic variants. [ABSTRACT FROM AUTHOR]

Biallelic mutations in the GPD1 gene cause a rare autosomal recessive inherited disease known as transient infantile hypertriglyceridemia (OMIM #614480). To date, only five pathogenic variants have been reported in 15 patients from three studies. The clinical symptoms of the affected individuals present a certain degree of heterogeneity. Here, we describe a chinese adolescent patient who mainly presented with obesity, insulin resistance, fatty liver, and short stature. Targeted next-generation sequencing revealed a novel compound heterozygous variant in GPD1 gene (c.220-2A>G and c.820G>A; p.Ala274Thr). In vitro studies demonstrated that the Ala274Thr variant induced a decrease in GPD1 protein expression. Further in vitro investigation of the splicing pattern in a minigene construct in HEK293 cells showed that the c.220-2A>G variant generated an altered transcript with one cryptic splice site in exon 3, resulting in the loss of 69 bases in exon 3 (c.220_288del, p.74_96del). This is the first report involving an Asian who harbored GPD1 mutations. Our work not only expands the mutant spectrum of the GPD1 gene but also provides new insights on its resulting phenotype. [ABSTRACT FROM AUTHOR]

Neurofibromatosis 1 ( NF1) is a common autosomal dominant condition caused by mutations in the NF1 gene. The appearance of multiple café-au-lait macules is an early sign of the condition, which often alert physicians to follow up and further examine the patient for the possibility of NF1. In order to determine the predictive value of multiple café-au-lait macules at early age for NF1 in Chinese patients, we recruited 19 children who shared the common sign of multiple café-au-lait macules from a general pediatric clinic in Shanghai. All the patients were clinically evaluated following the National Institutes of Health criteria for NF1 and molecular tested for sequence variants and copy number changes. Nine children met the clinical diagnostic criteria of NF1, and molecular tests confirmed all nine patients with pathogenic variants including two genomic deletions, two novel frame-shift variants, four novel nonsense and a splicing variants. In addition, four children who did not meet the diagnostic criteria were also found to carry pathogenic NF1 variants. Overall, 68.4% (13/19) of children with café-au-lait macules and various other clinical presentations were molecularly confirmed with NF1. This study demonstrated that the majority of Chinese children with multiple café-au-lait macules who came to seek for medical attention had NF1. Molecular testing is necessary to be used as an adjunct and sometimes as the main tool for confirming and diagnosing children of NF1 at early age. [ABSTRACT FROM AUTHOR]

Abstract: Chromosome 1p36 deletion is the most common subtelomeric deletion syndrome characterized by variable features including unique facial appearance, intellectual disability, developmental delay, cardiac defects, seizures and hypotonia. Here, we report a patient with developmental delay, dilated cardiomyopathy, seizures, hirsutism and cutis laxa who was diagnosed with 1p36 deletion syndrome by chromosome microarray analysis. This patient is the first reported case of 1p36 deletion syndrome associated with cutis laxa and our results suggest that the 1p36 region contains one or more genes relevant to cutis laxa. This case also indicates the importance of considering chromosome abnormalities (microdeletion/microduplication syndromes) in patients presenting skin disorders combined with unexplained developmental delay, intellectual disability or multiple congenital abnormalities. [ABSTRACT FROM AUTHOR]

Summary HIF‐2α, encoded by EPAS1, plays a dominant role in regulating erythropoietin (EPO) production, maintaining the dynamic balance of erythropoiesis. Gain‐of‐function mutations in EPAS1 cause erythrocytosis. However, anaemia caused by EPAS1 loss‐of‐function mutations has been confined to only one case report, and the underlying mechanism remains unclear. Herein, the reanalysis of high‐throughput sequencing data from 311 patients with anaemia identified three monoallelic EPAS1 variants from three unrelated families in a paediatric anaemia cohort. The probands showed highly consistent clinical phenotypes with normocytic and normochromic anaemia, reticulocytopenia and relative deficiency of serum EPO, characterised as congenital hypoplastic anaemia. In vitro studies suggested that defects in steady‐state protein abundance, nuclear localisation and binding with co‐activator in EPAS1 variants lead to impaired EPO transcriptional activation. Therefore, loss‐of‐function mutations in EPAS1 can cause erythroid hypoplasia in an EPO‐dependent manner. This study identified a new causative gene for congenital hypoplastic anaemia and clarified the molecular aetiology of loss‐of‐function EPAS1 mutations. [ABSTRACT FROM AUTHOR]

Background: Targeted gene capture and next‐generation sequencing (NGS) has been widely utilized as a robust and cost‐effective approach for detecting small variants among a group of disease genes. Copy number variations (CNV) can also be inferred from the read‐depth information but the accuracy of CNVs called from panel‐based NGS data has not been well evaluated. Methods: Sequencing data were acquired from patients underwent routine clinical targeted panel sequencing testing. Pathogenic CNVs detected from targeted panel sequencing data were evaluated using CNVs generated by two clinical accepted platforms, namely chromosome microarray analysis (CMA) and multiple ligation‐dependent probe amplification (MLPA) as benchmarks. CNVkit was used in our study to call CNVs from sequencing data using read‐depth information. CMA and MLPA tests were used to confirm and further assess the size and breakpoints of CNVs. Results: The size of CNVs detected using panel‐based NGS data are over 300 kb. The sizes of CNVs detected are slightly larger (102.3% on average) using the NGS platform than using the CMA platform, and the size accuracy improved as the size of variants increases. The breakpoints of CNVs detected using NGS data are quite close (within 2.3% of margin) to the breakpoints detected by CMA. CNVs on sex chromosomes, however, are less concordant between NGS and CMA platforms. Conclusion: Copy number variations covering adequate exons on autosomes can be accurately detected using targeted panel sequencing data as using CMA. CNVs detected from sex chromosomes need further evaluation and validation. Except for exon‐level deletion/duplication and CNV on sex chromosome, our data support the use of panel‐based NGS data for routine clinical detection of pathogenic CNVs. Copy number variations (CNV) detection based on panel‐based sequencing was comprehensively evaluated with clinical patients' data using chromosomal microarray and multiple‐ligation probe amplification as standards. CNVs larger than 600 kb on autosomes can be accurately detected using targeted panel sequencing data as using chromosome microarray. CNVs detected from sex chromosomes need further evaluation and validation. [ABSTRACT FROM AUTHOR]