Detection rate and clinical significance of regions of homozygosity in prenatal genetic diagnosis / 中华妇产科杂志

Objective:To detect the incidence and analyze the clinical significance of regions of homozygosity (ROH) through the single nucleotide polymorphism array (SNP array).Methods:The SNP array detection results of 5 116 pregnant women in the Third Affiliated Hospital of Guangzhou Medical University from January 2016 to December 2020 were retrospectively analyzed. The pregnant women with ROH (5 Mb as the threshold) were followed up to analyze the relationship between ROH and abnormal fetal phenotype. Whole exon sequencing was performed in 4 cases of consanguineous marriage to detect potential recessive causative genes in the ROH region.Results:(1) A total of 39 cases of ROH were detected, with a positive rate of 0.76% (39/5 116). Among them, 25 cases (64%, 25/39) were detected only on single chromosome, and chromosome 11 had the highest detection rate, suggesting the risk of uniparental disomy; fourteen cases (36%,14/39) were detected on multiple chromosomes, most commonly on chromosomes 11, 1, 3, 4 and 8. (2) The number of cases and detection rate of ROH detected by different prenatal diagnosis indicators were as follows: 12 cases (1.78%, 12/676) in pregnant women with abnormal non-invasive prenatal testing result, 12 cases (0.37%, 12/3 284) in pregnant women with ultrasound abnormality, 4 cases (4/4) in pregnant women with consanguineous marriage, 3 cases (0.92%, 3/326) in pregnant women with previous adverse pregnancy, 2 cases (1.15%, 2/174) in pregnant women with high risk of serology in screening, 2 cases (4.00%, 2/50) in pregnant women with abnormal fetal chromosomal karyotype, 2 cases (0.79%, 2/253) in pregnant women with advanced maternal age, 1 case (0.56%, 1/178) in pregnant women with related parental genetic factors and 1 case (0.58%, 1/171) in pregnant women with the other factors. (3) The follow-up results of 39 cases of prenatal ROH showed that there were 16 cases of term birth, 15 cases of termination of pregnancy, 2 cases of preterm births, 1 case of fetal death and 5 cases lost to follow-up.Conclusions:Chromosomal ROH phenomenon is not rare. By analyzing the detection rate of ROH in prenatal diagnosis, combined with the results of fetal phenotype and postpartum follow-up, the clinical characteristics of ROH are discussed, so as to better understand the relationship between ROH and its phenotype.

A de novo marker chromosome 15 in a child with isolated developmental delay

We report a rare case of a 14-month-old male child who was referred for developmental delay. Clinical examination revealed a hypotonic infant with speech delay and no dysmorphic features. The banding cytogenetics revealed a small supernumerary marker chromosome. Upon silver staining, the marker showed the presence of satellite regions on either ends. Further, analysis using fluorescence in situ hybridization on marker chromosome revealed its origin from chromosome 15.

Genetic analysis of an adult with mosaicism of uniparental disomy 11p / 中华医学遗传学杂志

Objective@#To analyze the clinical phenotype and genomic abnormality of an adult featuring congenital heart defect and multiple developmental disorders.@*Methods@#The patient was subjected to conventional G-banding chromosomal karyotyping and single nucleotide polymorphism microarray (SNP-array) analysis.@*Results@#The patient showed a normal karyotype, while SNP-array revealed a 42.7 Mb mosaic uniparental disomy (UPD) in the 11p15.5p12 region ([hg19] chr11: 491 333 - 43 189 376).@*Conclusion@#The mosaicism of UPD of 11p15.5p12 region probably underlies the congenital heart defect and developmental disorders in the patient.

Influence of uniparental disomy on the conclusion of paternity testing / 中华医学遗传学杂志

Objective@#To explore the influence of uniparental disomy (UPD) on bipartite and tripartite paternity testing.@*Methods@#Two cases of paternity testing were analyzed by multiplex amplification and capillary electrophoresis typing. Suspected UPD was verified by using single nucleotide polymorphism array (SNP array). Parental power index was calculated by using a bipartite or tripartite model.@*Results@#The two cases were found to harbor respectively three short tandem repeats on chromosome 2 and two short tandem repeats on chromosome 15. SNP array verified that both cases were of UPD. Case 1 had a parental power index of 122274987565.23 by a tripartite model, while case 2 had a parental power index of 13500.8463 by a bipartite model. Based on the technical specification, the conclusions supported a biological parent-child relationship in both cases.@*Conclusion@#UPD may lead to misjudgment of paternity testing. The possibility of UPD should be considered when certain loci which do not conform to Mendelian inheritance have aggregated to one chromosome.

The chromosome abnormality in forensic DNA test / 复旦学报（医学版）

Chromosome abnormality is a serious congenital disease,which was usually researched in genetic diseases and prenatal diagnosis.In recent years,some special STR profile and pseudo-exclusion case caused by abnormal chromosome are found in forensic DNA test.We reviewed several common chromosome abnormality contained trisomy syndrome,uniparental disomy and Chimera were reported in forensic medicine to provide reference for forensic DNA workers.

A case of maternal uniparental disomy of chromosome 20 detected by noninvasive prenatal test of 1,000 high-risk pregnancies

Chromosomal loss in trisomy (trisomy rescue) to generate a disomic fetus can cause confined placental mosaicism and/or feto/placental mosaicism. After trisomy rescue event, there is a risk of fetal uniparental disomy (UPD). Noninvasive prenatal test (NIPT) reflects the genomic constitution of the placenta, not of the fetus itself. Feto-placental discrepancy can therefore cause false-positive (trisomy) NIPT results. These discordant NIPT results can serve as important clues to find UPD associated with confined placental mosaicism. We report a case with maternal UPD of chromosome 20, detected by NIPT of 1,000 high-risk pregnancies, carried out for detecting chromosomal abnormalities in Koreans.

A Unique Mutational Spectrum of MLC1 in Korean Patients With Megalencephalic Leukoencephalopathy With Subcortical Cysts: p.Ala275Asp Founder Mutation and Maternal Uniparental Disomy of Chromosome 22

BACKGROUND: Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare inherited disorder characterized by infantile-onset macrocephaly, slow neurologic deterioration, and seizures. Mutations in the causative gene, MLC1, are found in approximately 75% of patients and are inherited in an autosomal recessive manner. We analyzed MLC1 mutations in five unrelated Korean patients with MLC. METHODS: Direct Sanger sequencing was used to identify MLC1 mutations. A founder effect of the p.Ala275Asp variant was demonstrated by haplotype analysis using single-nucleotide polymorphic (SNP) markers. Multiple ligation-dependent probe amplification (MLPA) and comparative genomic hybridization plus SNP array were used to detect exonic deletions or uniparental disomy (UPD). RESULTS: The most prevalent pathogenic variant was c.824C>A (p.Ala275Asp) found in 7/10 (70%) alleles. Two pathogenic frameshift variants were found: c.135delC (p.Cys46Alafs*12) and c.337_353delinsG (p.Ile113Glyfs*4). Haplotype analysis suggested that the Korean patients with MLC harbored a founder mutation in p.Ala275Asp. The p.(Ile113Glyfs*4) was identified in a homozygous state, and a family study revealed that only the mother was heterozygous for this variant. Further analysis of MLPA and SNP arrays for this patient demonstrated loss of heterozygosity of chromosome 22 without any deletion, indicating UPD. The maternal origin of both chromosomes 22 was demonstrated by haplotype analysis. CONCLUSIONS: This study is the first to describe the mutational spectrum of Korean patients with MLC, demonstrating a founder effect of the p.Ala275Asp variant. This study also broadens our understanding of the mutational spectrum of MLC1 by demonstrating a homozygous p.(Ile113Glyfs*4) variant resulting from UPD of chromosome 22.

Unexpected Inheritance of a Balanced Homologous translocation t(22q;22q) from father to a phenotypically normal daughter.

Rearrangements between homologous chromosomes are extremely rare and manifest mainly as monosomic or trisomic offsprings. There are remarkably few reports of balanced homologous chromosomal translocation t (22q; 22q) and only two cases of transmission of this balanced homohologous rearrangement from mother to normal daughter are reported. Robersonian translocation carriers in non‑homologous chromosomes have the ability to have an unaffected child. However, it is not possible to have an unaffected child in cases with Robersonian translocations in homologous chromosomes. Carriers of homologous chromosome 22 translocations with maternal uniparental disomy do not have any impact on their phenotype. We are presenting a family with a history of multiple first trimester miscarriages and an unexpected inheritance of balanced homologous translocation of chromosome 22 with paternal uniparental disomy. There are no data available regarding the impact of paternal UPD 22 on the phenotype. We claim this to be the first report explaining that paternal UPD 22 does not impact the phenotype.

Pattern of chromosome involvement in childhood hyperdiploid pre-B-cell acute lymhoblastic leukemia cases from India.

BACKGROUND: Hyperdiploid pre‑B‑cell acute lymhoblastic leukemia (pre‑B‑ALL) is a common form of childhood leukemia with very good prognosis with present day chemotherapy. However, the chromosomal composition of the hyperdiploidy has not been extensively studied and possible mechanism for this pathology remains so far conjectural. OBJECTIVE: To analyze the pattern of chromosome involvement in a cohort of childhood hyperdiploid pre‑B‑ALL from India and from this pattern to develop an understanding on the causation of such pathology. Whether such patients also carry translocations and FLT3 mutations in addition to their hyperdiploid karyotype. MATERIALS AND METHODS: One hundred and twenty‑six childhood pre‑B‑ALL patients were studied. Bone marrow aspirate of these patients were evacuated for morphology, FAB classification, immunophenotyping and both conventional and molecular cytogenetics. RESULTS: Of 126 patients with pre‑B‑ALL (age 2-15 years), 90 patients with abnormal karyotype showed 50 with hyperdiploid karyotype (50/90 i.e. 55.5%). Chromosomes 9, 10, 14, 17, 18, 20 and 21 were more often involved in hyperdiploidy. Chromosome 21 duplication was present in 92% of the cases. Chromosomes 5, 15, 16, 17 and Y were less often involved (18-20%) in hyperdiploidy. About 44% of patients with hyperdiploidy had additional karyotypic abnormality of which TEL‑AML1 was predominant (24%). Chromosome loss was rare and accounted for 20% of the cases only. We did not find any FLT3 mutation in our patients. CONCLUSION: In this study, the pattern of chromosome involvement in hyperdiploid karyotype of ALL patients is same as other studies except some chromosomes like 1, 6, 11, 12, 19 and 22 have some more frequent involvement than other studies. This study also showed the occurrence of TEL/AML1 fusion is more (19.8%) than other reports from India.

Phenotypic spectrum in uniparental disomy: Low incidence or lack of study.

CONTEXT: Alterations in the human chromosomal complement are expressed phenotypically ranging from (i) normal, via (ii) frequent fetal loss in otherwise normal person, to (iii) sub‑clinical to severe mental retardation and dysmorphism in live births. A subtle and microscopically undetectable chromosomal alteration is uniparental disomy (UPD), which is known to be associated with distinct birth defects as per the chromosome involved and parental origin. UPD can be evident due to imprinted genes and/or activation of recessive mutations. AIMS: The present study comprises of data mining of published UPD cases with a focus on associated phenotypes. The goal was to identify non‑random and recurrent associations between UPD and various genetic conditions, which can possibly indicate the presence of new imprinted genes. SETTINGS AND DESIGN: Data mining was carried out using the homepage “http://www.fish.uniklinikum‑jena.de/ UPD.html,” an online catalog of published cases with UPD. MATERIALS AND METHODS: The UPD cases having normal karyotype and with or without clinical findings were selected to analyze the associated phenotypes for each chromosome, maternal or paternal involved in UPD. RESULTS: Our results revealed many genetic conditions (other than the known UPD syndromes) to be associated with UPD. Even in cases of bad obstetric history as well as normal individuals chance detection of UPD has been reported. CONCLUSIONS: The role of UPD in human genetic disorders needs to be studied by involving larger cohorts of individuals with birth defects as well as normal population. The genetic conditions were scrutinized in terms of inheritance patterns; majority of these were autosomal recessive indicating the role of UPD as an underlying mechanism.

Growth Hormone Treatment and Its Effect on Height in Pediatric Patients with Different Genotypes of Prader-Willi Syndrome

PURPOSE: Differences in phenotypes between the two most common subtypes of Prader-Willi syndrome (PWS) indicate that a distinct response to growth hormone (GH) treatment may exist. To test this hypothesis, we compared the results of GH treatment in individuals with PWS due to uniparental disomy (UPD) to those of individuals with deletions. METHODS: Sixty-five children with PWS who had been treated with GH for more than two years were included in this study. Twenty-one individuals were confirmed as having UPD and 44 individuals had a deletion. Height, body weight, body mass index (BMI), and insulin like growth factor-1 (IGF-I) measurements were recorded before GH treatment and at intervals of 12 months thereafter. RESULTS: After two years of GH therapy, no significant differences were noted for yearly improvements in height standard deviation scores (SDS) between the groups (second year SDS, 0.93 +/- 0.94; deletion, 0.84 +/- 1.31; UPD, P = 0.717). Body weight SDS, BMI SDS, and IGF-I SDS also showed no differences between the two groups. CONCLUSION: Our study showed no significant differences in yearly improvements in height SDS between the deletion and UPD groups, at least for the first two years.

Growth Hormone Treatment and Its Effect on Height in Pediatric Patients with Different Genotypes of Prader-Willi Syndrome

PURPOSE: Differences in phenotypes between the two most common subtypes of Prader-Willi syndrome (PWS) indicate that a distinct response to growth hormone (GH) treatment may exist. To test this hypothesis, we compared the results of GH treatment in individuals with PWS due to uniparental disomy (UPD) to those of individuals with deletions. METHODS: Sixty-five children with PWS who had been treated with GH for more than two years were included in this study. Twenty-one individuals were confirmed as having UPD and 44 individuals had a deletion. Height, body weight, body mass index (BMI), and insulin like growth factor-1 (IGF-I) measurements were recorded before GH treatment and at intervals of 12 months thereafter. RESULTS: After two years of GH therapy, no significant differences were noted for yearly improvements in height standard deviation scores (SDS) between the groups (second year SDS, 0.93 +/- 0.94; deletion, 0.84 +/- 1.31; UPD, P = 0.717). Body weight SDS, BMI SDS, and IGF-I SDS also showed no differences between the two groups. CONCLUSION: Our study showed no significant differences in yearly improvements in height SDS between the deletion and UPD groups, at least for the first two years.

Phenotype-genotype correlations and the efficacy of growth hormone treatment in Korean children with Prader-Willi syndrome / 소아과

PURPOSE: Prader-Willi syndrome (PWS) is a complex genetic disorder, caused by the deletion of the paternally derived 15q11-13 region or the maternal uniparental disomy of chromosome 15 (mUPD(15)). In this study, we compared phenotypic differences between those patients whose disease was caused by microdeletion and those caused by mUPD(15). In addition, a comparison of the efficacy of growth hormone (GH) therapy between these two PWS genotypes was analyzed. METHODS: Fifty-three patients were diagnosed as having PWS based on molecular and cytogenetic analyses and clinical features. Data that included maternal age, birth weight, a feeding problem in the neonatal period, cryptorchidism, developmental delay or mental retardation, short stature, hypopigmentation, changes in height, weight, and body mass indexes (BMI) before and after GH treatment were obtained by a retrospective review of medical records. The data from the patients with microdeletion were compared with those from the patients with mUPD(15). RESULTS: Of the 53 patients with genetically confirmed PWS, 39 cases had microdeletion and 14 mUPD(15). Maternal ages were significantly higher in the mUPD(15) group, and hypopigmentation and a feeding problem in the neonatal period were more frequent in the microdeletion group. Growth hormone was administered to 20 patients [14 with microdeletion, 6 with mUPD(15)]. There were no differences between the two groups in height velocity, weight and height SDS, and BMI after GH therapy. CONCLUSION: Phenotype and genotype correlations were observed in Korean PWS patients, such as more advanced maternal ages in the mUPD(15) group and more feeding problems and hypopigmentations in the microdeletion group. Further long-term prospective studies are needed to correlate other aspects of the phenotypes.

Two Cases of Transient Neonatal Diabetes Mellitus in Twin Brothers / 대한소아내분비학회지

Neonatal diabetes mellitus (NDM) is defined as hyperglycemia that presents clinical symptoms within the first month of life and requires insulin therapy to maintain euglycemia. The diabetic condition may be transient, permanent, or transient with recurrence later in life. NDM is a rare clinical disorder. Three cases of NDM have been reported in Korea so far. We experienced two cases of NDM in twin brothers who were born with small for gestational ages. Their HLA typings were DR9 and DR14, and insulin autoantibody, islet cell antibody, GAD-reactive autoantibody, and insulin receptor antibody were not found. The genetic analysis with polymorphic DNA markers for chromosome 6 indicated paternal uniparental isodisomy.