TARS2 c.470 C > G is a chinese-specific founder mutation in three unrelated families with mitochondrial encephalomyopathy.

Biallelic pathogenic variants in TARS2 lead to combined oxidative phosphorylation deficiency, subtype 21 (COXPD21, MIM #615918), which is a rare mitochondrial encephalomyopathy (ME) characterized by early-onset severe axial hypotonia, limb hypertonia, psychomotor developmental delay, epilepsy and brain anomalies. To date, approximately 28 individuals with COXPD21 and 28 TARS2 variants have been identified. In this study, we reported additional four individuals from three unrelated Chinese families with mitochondrial encephalomyopathy caused by pathogenic variants in TARS2, and described the novel clinical phenotypes and genotypic information. In addition to two novel variants (c.512G > A, p.Arg171Lys; c.988dup, p.Arg330Lysfs*4), one previously reported variant (c.470 C > G, p.Thr157Arg) recurred in six Chinese individuals with COXPD21 but was not present in populations of other races. Our findings expanded the mutation spectrum of TARS2 and confirmed that c.470 C > G is a Chinese-specific founder mutation. The novel phenotypes, including reduced fetal movement, eye anomalies and sleep irregularities, observed in our patients enriched the clinical characteristics of COXPD21.

De novo variants in genes regulating stress granule assembly associate with neurodevelopmental disorders.

Stress granules (SGs) are cytoplasmic assemblies in response to a variety of stressors. We report a new neurodevelopmental disorder (NDD) with common features of language problems, intellectual disability, and behavioral issues caused by de novo likely gene-disruptive variants in UBAP2L, which encodes an essential regulator of SG assembly. Ubap2l haploinsufficiency in mouse led to social and cognitive impairments accompanied by disrupted neurogenesis and reduced SG formation during early brain development. On the basis of data from 40,853 individuals with NDDs, we report a nominally significant excess of de novo variants within 29 genes that are not implicated in NDDs, including 3 essential genes (G3BP1, G3BP2, and UBAP2L) in the core SG interaction network. We validated that NDD-related de novo variants in newly implicated and known NDD genes, such as CAPRIN1, disrupt the interaction of the core SG network and interfere with SG formation. Together, our findings suggest the common SG pathology in NDDs.

The application of expanded noninvasive prenatal screening for genome-wide chromosomal abnormalities and genetic counseling.

OBJECTIVE: To evaluate the clinical application of expanded noninvasive prenatal screening (eNIPS) for genome-wide large copy number variation (CNV), i.e. chromosomal deletion/duplication >5 Mb, and aneuploidy; also to provide practical information for counseling eNIPS positive cases. METHOD: We recruited 34,620 women with singleton pregnancy for genome-wide cell-free plasma DNA sequencing. Screening positive cases were verified by karyotyping and/or SNP array. RESULT: A total of 461 (1.33%) positive cases were identified through our cfDNA screening including 209 cases of common trisomies (0.60%), 124 cases of sex chromosomal abnormalities (SCA) (0.36%), 71 cases of other autosomal anueploidies (OAA) (0.21%), and 57 CNVs larger than 5 Mb (0.16%). The predictive positive values (PPV) were 70.06% in general for common trisomies with as high as 91.67% for Trisomy21 (T21), 40.22% in general for SCAs with as high as 100% for Jacob Syndrome (XYY). The PPV for OAAs was 5.45%, and T7/T8/T16/T22 were the most frequent OAAs (n = 15, 9, 9, 8, respectively). The PPV for CNVs larger than 5 Mb was 51.22% (n = 57) with the CNV mostly detected on Chr5/Chr4/Chr2/Chr7 (n = 10, 8, 5, 5, respectively). CONCLUSION: The expanded NIPS had shown promising PPVs for CNVs (large than 5 Mb), SCAs and common trisomies, yet this method required higher efficacy in screening for OAAs. The post-test genetic counseling for expanded NIPS should be tailored to the types of positive cases and also address the origin of abnormal signals (fetal vs. maternal).

Novel genotypes and phenotypes among Chinese patients with Floating-Harbor syndrome.

BACKGROUND: Floating-Harbor syndrome (FHS) is a rare syndromic short stature disorder caused by truncating variants in SRCAP. Few Chinese FHS patients had been reported so far and limited knowledge regarding the benefit of growth hormone treatment existed. METHODS: We ascertained 12 short stature patients with molecularly confirmed diagnosis of FHS by whole exome sequencing. We performed a comprehensive clinical evaluation for all patients and assessed the responsiveness of growth hormone treatment in a subset of the patients. RESULTS: Five distinct pathogenic/likely pathogenic variants were identified in 12 independent FHS patients including two previously reported variants (c.7303C > T/p.Arg2435Ter and c.7330C > T/p.Arg2444Ter) and three novel variants (c.7189G > T/p.Glu2397Ter, c.7245_7246delAT/p.Ser2416ArgfsTer26 and c.7466C > G/p.Ser2489Ter). The c.7303C > T/p.Arg2435Ter mutation appears more common in Chinese FHS patients. The clinical presentations of Chinese FHS patients are very similar to those of previously reported patients of different ethnicities. Yet we noticed micropenis and ear abnormalities in multiple patients, suggesting that these may be novel phenotypes of Floating-Harbor syndrome. Eight patients (one with GH deficiency, one with undetermined GH level, six without GH deficiency) underwent growth hormone treatment, 3 patients had good responses, one with modest and two with poor responses. CONCLUSION: We described novel genotypes and phenotypes in a Chinese FHS patient cohort. We showed that about half of FHS patients exhibited modest to good response to GH treatment regardless of their respective GH deficiency status. We didn't find any correlation between different mutations and response to GH treatment.

[Application of SNP-array technology in the genetic analysis of pediatric patients with growth retardation].

OBJECTIVE: To explore the value of single nucleotide polymorphism array (SNP-array) for the analysis of pediatric patients with growth retardation. METHODS: One hundred eighty one children with growth retardation were enrolled. DNA was extracted from peripheral samples from the patients, and whole genome copy number variations (CNVs) were detected using Illumina Human Cyto SNP-12. All identified CNVs were further analyzed with reference to databases including ClinGen, ClinVar, DECIPHER, OMIM and DGV as well as comprehensive review of literature from PubMed to determine their pathogenicity. RESULTS: Forty seven patients (26%) with abnormal CNVs were detected, which included 12 known microdeletions/microduplications syndrome (26%), 10 pathogenic non-syndromic CNVs (21%), 3 numerical chromosome aberrations (6%), 3 unbalanced translocations (6%), 4 pathogenic mosaicisms (9%) and 15 cases with unknown clinical significance (32%). After excluding obvious numerical and/or structural chromosomal abnormalities, this study has detected 15 pathogenic microdeletions/microduplications sized 5 Mb or less, which may be missed by routine chromosomal karyotyping. In addition, there were 3 cases with loss of heterozygoisty (LOH) containing known or predicted imprinting genes as well as 2 cases with suspected parental consanguinity. CONCLUSION: SNP-array technology is a powerful tool for the genetic diagnosis of children with growth disorders with advantages of high resolution and improved accuracy.

Maternal uniparental disomy 14 and mosaic trisomy 14 in a Chinese boy with moderate to severe intellectual disability.

BACKGROUND: Both maternal uniparental disomy 14 (UPD(14)mat) and mosaic trisomy 14 are rare events in live individuals. A combination of the two events in one individual is rarely encountered. Only six live-born cases have so far been reported. CASE PRESENTATION: Here we reported a case of concomitant UPD(14)mat and mosaic trisomy 14 in a 10-year-old Chinese patient. Most clinical features of our patient were consistent with those previous reported for UPD(14)mat cases, which include prenatal and postnatal growth retardation, neonatal hypotonia, feeding difficulty, intellectual disability, truncal obesity, small hands and feet, short stature, and mild facial dysmorphism, but our patient showed more severe intellectual disability and no sign of precocious puberty. SNP array analysis revealed a mixture of chromosome 14 maternal isodisomy with heterodisomy and a low level trisomy mosaicism of whole chromsome 14 in blood and hyperpigmented skin samples, whereas only UPD(14)mat was detected in normal skin sample. Cytogenetic analysis identified one trisomy 14 cell in 100 metaphase of peripheral blood lymphocytes (47,XX, +14[1]/46,XX[99]). CONCLUSIONS: To our knowledge, this is the first case of a patient with UPD(14)mat and mosaic trisomy 14 reported in a Chinese patient. The definitive genetic diagnosis is beneficial for genetic counseling and clinical management of our patient, and for improving our understanding of the genotype-phenotype correlations of concomitant UPD(14)mat and mosaic trisomy 14.

Novel and reported APC germline mutations in Chinese patients with familial adenomatous polyposis.

OBJECTIVE: Familial adenomatous polyposis (FAP) is mainly caused by germline mutations in the adenomatous polyposis coli (APC) gene. This study aimed to detect pathogenic variants in five Chinese FAP families and review all previously reported pathogenic variants of APC gene in Chinese population. METHODS: Five non-consanguineous FAP families and 100 unrelated ethnicity-matched controls were included in the study. Sanger sequencing was performed to screen for APC coding and splicing variants. Chinese and English literature on APC germline mutations were reviewed to compile the mutation spectrum of APC gene in Chinese FAP patients. RESULTS: One pathogenic variant was detected in each family for the five pedigrees we tested. Three variants (c.3183_3187delACAAA, c.2626C>T and c.1312+1G>A) were previously reported as pathogenic. The other two variants were novel: c.794_795insG/p.Val266SerfsTer11 and c.2142_2143insG/p.His715AlafsTer19. They are absent from public databases (1000 Genomes, dbSNP, ESP and ExAC) and 100 normal controls, and are classified as pathogenic based on the new ACMG/AMP variant classification guidelines. Literature review and current study revealed a total of 82 different pathogenic variants from 127 Chinese FAP families. Among these families, 83 families had frameshift variants (65.35%), 26 with nonsense variants (20.47%), six with splice site variants (4.72%), three with missense variants (2.36%) and nine with large deletion or duplication variants (7.09%). Apart from the two previously reported mutation hotspots c.3927_3931delAAAGA (20.47%) and c.3183_3187delACAAA (7.09%), c.847C>T/p.Arg283Ter variant occurred with a frequency of 3.15% (4 out of 127) in Chinese FAP patients. CONCLUSIONS: We reported two novel pathogenic variants. The comprehensive compilation of variants and comparison revealed largely similar mutation spectrum between Chinese and Western patient populations. Some unique features noticed in Chinese patient population may help to better understand the pathogenesis of FAP.