Phenotypic Spectrum of Trisomy 18 Mosaicism: a New Patient and Literature Review.

BACKGROUND: Trisomy 18 syndrome, also called Edwards syndrome, is the second most common autosomal trisomy after trisomy 21 that is caused by the presence of an extra copy of chromosome 18. Approximately 50% of infants with trisomy 18 cannot survive for more than 1 week and about 5 - 10% of children die within 1 year after birth. The aim of this study is to describe a 4-year-old female patient of mosaic trisomy 18 with normal prenatal ultrasound findings and maternal serum markers and to investigate the relationship between the percentage of trisomic cells and the major clinical phenotypes combined with other nine patients through a review of the literature. METHODS: The patient's peripheral blood was examined by cytogenetic G-banding technique. RESULTS: The cytogenetics results reported following the ISCN 2020 guideline as mos 47,XX,+18[87]/46,XX[13]. CONCLUSIONS: There is little correlation between various phenotypes of mosaic trisomy 18 and the percentage of trisomy cells in the patient's peripheral leukocytes. Although most of fetuses with mosaic trisomy 18 have abnormal ultrasound findings, it is necessary to highlight the possibility of normal findings during the pregnancy.

[Application of flat-sided culture tubes during prenatal diagnosis].

OBJECTIVE: To assess the value of using flat-sided culture tubes for preparing chromosomes through chorionic villi (CV) and amniotic fluid (AF) cell cultures during prenatal diagnosis. METHODS: From February to March 2020, 157 CV samples and 147 AF samples subjected to prenatal diagnosis at the Maternal and Child Health Care Hospital of Guangxi Zhuang Autonomous Region were selected as the study subjects. For each sample, one flat-sided tube and one flask culture were set up by following the standard protocols. The methods were evaluated by comparing the cell growth, experimental process, quality of chromosome preparation and costs. RESULTS: The success rates for the culturing of CV and AF samples by the flat-sided culture tube method were 97.45% (153/157) and 97.96% (144/147), respectively. By contrast, the success rates for the conventional flask method were 98.72% (155/157) for CV and 98.64% (145/147) for AF samples. No significant difference was found between the two methods (P > 0.05). The average harvest time required by the flat-sided culture tube method was 8.45 days for CV and 9.43 days for AF cultures, whilst the average harvest time for conventional flask method was 9.05 days and 9.54 days, respectively. The flat-sided culture tube method for CV had required significantly shorter average harvest time than the conventional method (P < 0.001). No statistical significant difference was found in the average harvest time for AF by the two methods (P > 0.05). The conventional culturing method had required three containers with two sample transfers. By contrast, the flat-sided culture tube method was carried out in one tube without any sample transfer. The average total amount of medium used was 3.91 mL for each flat-sided culture tube and 6.26 mL for each conventional flask. CONCLUSION: The flat-sided culture tube method can provide a simple, cost-effective and error-reducing procedure for the CV and AF samples culture during prenatal diagnosis.

[Comparison of performance of two prenatal diagnostic techniques for the detection of chromosomal mosaicisms in amniocytes].

OBJECTIVE: To assess the value of chromosomal karyotyping analysis and single nucleotide polymorphism-based microarray (SNP-array) for the detection of chromosomal mosaicisms in amniotic fluid samples. METHODS: Seventy four pregnant women with fetal mosaicisms detected by both methods were retrospectively analyzed. RESULTS: Among the 74 mosaicisms, 12 were pseudo and 62 were true mosaicisms, which included 1 Robertsonian translocation, 3 deletions, 4 supernumerary markers, 19 autosomal aneuploidy mosaicisms, 30 sex chromosome aneuploidy mosaicisms and 5 isometric chromosome mosaicisms. CONCLUSION: Chromosome karyotyping analysis and SNP-array have their own advantages and limitations for the diagnosis of mosaicisms. When the two methods have yielded inconsistent results, fluorescence in situ hybridization may be used for further verification.

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.

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.

A rare occurrence of two large de novo duplications on 1q42-q44 and 9q21.12-q21.33.

De novo partial distal 1q trisomy is uncommon and mostly occurs in combination with monosomy of another chromosome due to a parental translocation. Distal 1q trisomy co-occurring with another de novo duplication on a separate chromosome is extremely rare. Here, we reported a patient carrying two large de novo interstitial duplications including a 20Mb duplication at 1q42-q44 and a 14.2Mb duplication at 9q21.12-q21.33. The patient presented with features of pre- and postnatal growth retardation, low birth weight, failure to thrive, developmental delay and frequent infection. Her dysmorphic features included macrocephaly, prominent forehead, triangular face, wide fontanelle, hypertelorism, flat nasal bridge, tented mouth, micrognathia, protruding and low-set ears, slender limbs with toe-walking appearance. In addition, she presented with subdural hematoma. The clinical presentations of this patient are mostly consistent with those of distal 1q trisomy syndrome or 9q interstitial duplication. The interstitial 1q trisomy may have contributed to the macrocephaly, prominent forehead and limb abnormalities of our patient. Either or both de novo duplications could have contributed to the features of growth retardation, developmental delay and dysmorphic features including hypertelorism, low-set ears and abnormal nose/nasal bridge.