OBJECTIVE: To explore the clinical and genetic characteristics of a boy with isolated maternal uniparental disomy of chromosome 20 [UPD(20)mat]. METHODS: A child who was admitted to the Tongji Hospital Affiliated to Tongji Medical College of Huazhong University of Science and Technology on April 8,2021. was selected as the study subject. Phenotypic and endocrinological findings of the child were retrospectively analyzed. Whole exome sequencing (WES) and methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) were carried out for detecting the UPD sequences and copy number variations. Both of his parents were verified by Sanger sequencing. Relevant literature was systematically reviewed. RESULTS: The child, a 3-year-and-8-month-old boy born to a 41-year-old mother by Cesarean delivery at 36⁺² gestational weeks due to oligohydramia, had a birth weight of 2 300 g and length of 46 cm. He was admitted to the NICU for feeding difficulties which had persisted despite of clinical management. At the age of 3.75, he had a height of 92.5 cm (< 3rd percentile; 25th ~ 50th percentile at 2.5 years) and a weight of 10.8 kg (< 3rd percentile; 50th percentile at 15 months). He had also presented with growth retardation, short stature, attention deficit and hyperactivity disorder (ADHD), mild mental retardation, and speech and language development disorders. He had simian creases in both hands but no additional dysmorphic signs, and his motor development was normal. Serum insulin, thyroid-stimulating hormone, and insulin growth factor binding protein 3 levels were within the normal ranges, though insulin growth factor-1 (IGF-1) was slightly decreased. Since that time he had continuously used atomoxetine hydrochloride capsules to control his ADHD. WES and MS-MLPA revealed the existence of UPD (20)mat. CONCLUSION The UPD(20)mat syndrome is characterized by feeding difficulties, growth retardation and short stature. The child in our case has been accompanied by ADHD and speech and language development disorders, which required long-term treatment. For women with advanced maternal age and suggestive phenotypes, genetic testing and counseling should be conducted.
Male ; Pregnancy ; Humans ; Child ; Female ; Infant ; Adult ; Chromosomes, Human, Pair 20 ; DNA Copy Number Variations ; Retrospective Studies ; Uniparental Disomy/genetics* ; Atomoxetine Hydrochloride ; Dwarfism ; Intercellular Signaling Peptides and Proteins ; Language Development Disorders ; Growth Disorders ; Insulins

OBJECTIVE: To carry out genetic analysis for a fetus with confined placental mosaicism (CPM) for trisomy 2 (T2) in conjunct with fetal uniparental disomy (UPD). METHODS: Amniocentesis and chromosomal karyotyping was carried out for a pregnant woman with a high risk for chromosome 2 anomalies indicated by non-invasive prenatal testing (NIPT). Single nucleotide polymorphism array (SNP-array) and trio-whole exome sequencing (Trio-WES) were carried out. Ultrasonography was used to closely monitor the fetal growth. Multifocal sampling of the placenta was performed after delivery for copy number variation sequencing (CNV-seq). RESULTS: The fetus was found to have a normal chromosomal karyotype. SNP-array has revealed multiple regions with loss of heterozygosity (LOH) on chromosome 2. Trio-WES confirmed the presence of maternal UPD for chromosome 2. Ultrasonography has revealed intrauterine growth restriction and oligohydramnios. Intrauterine fetal demise had occurred at 23⁺⁴ weeks of gestation. Pathological examination had failed to find salient visceral abnormality. The placenta was proved to contain complete T2 by CNV-seq. CONCLUSION T2 CPM can cause false positive result for NIPT and may be complicated with fetal UPD, leading to adverse obstetric outcomes such as intrauterine growth restriction, oligohydramnios and intrauterine fetal demise.
Female ; Humans ; Pregnancy ; Amniocentesis ; Chromosomes, Human, Pair 2/genetics* ; DNA Copy Number Variations ; Fetal Death ; Fetal Growth Retardation/genetics* ; Fetus ; Mosaicism ; Oligohydramnios ; Placenta ; Trisomy/genetics* ; Uniparental Disomy/genetics*

The overall prevalence of uniparental disomy (UPD) across all chromosomes was estimated to be around one birth in 2000. To date, more than 4170 UPD cases have been registered. UPD for chromosomes 6, 7, 11, 14, 15, and 20 can result in clinically recognizable imprinting disorders due to abnormal levels of imprinted gene expression. For other chromosomes, the clinical consequences associated with UPD are not apparent, unless when a recessive genetic disorder is unmasked by UPD or regions of homozygosity (ROH). A clinical practice guideline will assist in strengthening the precise analysis and interpretation of the clinical significance of ROH/UPD. This guideline summarizes the conception, mechanism and clinical consequences of ROH/UPD, as well as the principles for data analysis, with an aim to standardize the clinical application and data interpretation.
Gene Expression ; Genomic Imprinting ; Homozygote ; Humans ; Uniparental Disomy/genetics*

Uniparental disomy (UPD) refers to a chromosome defect that an individual's homologous chromosome or segments are inherited from one parent. UPD can cause either aberrant patterns of genomic imprinting or homozygosity of mutations, leading to various diseases, including cancer. The mechanisms of UPD formation are diverse but largely due to the incorrect chromosome separation during cell division. UPD does not alter the number of gene copies, thus is difficult to be detected by conventional cytogenetic techniques effectively. Assisted by the new techniques such as single nucleotide polymorphism arrays, more and more UPD-related cases have been reported recently. UPD events are non-randomly distributed across cancer types, which play important role in the occurrence, development and metastasis of cancer. Here we review the research progress on the formation mechanisms, detection methods, the involved chromosomal regions and genes, and clinical significance of UPD; and also discuss the directions for future studies in this field.
Genomic Imprinting ; Humans ; Neoplasms ; genetics ; Research ; trends ; Uniparental Disomy

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.
Chromosomes, Human, Pair 2 ; genetics ; Humans ; Microsatellite Repeats ; Paternity ; Polymorphism, Single Nucleotide ; Uniparental Disomy ; genetics

Patients with Beckwith-Wiedemann syndrome (BWS) are predisposed to developing embryonal tumors, with hepatoblastoma being the most common type. Our patient showed hemihypertrophy, macroglossia, and paternal uniparental disomy in chromosome 11 and was diagnosed with BWS. When the patient was 9 months old, a 2.5×1.5 cm oval hypoechoic exophytic mass was detected in the inferior tip of his right liver. Preoperative imaging identified it as hepatoblastoma; however, histologic, immunohistochemistry, and electron microscopic findings were compatible with adrenal cortical neoplasm with uncertain malignant potential. The origin of the adrenal tissue seemed to be heterotopic. Here, we describe for the first time an adrenal cortical neoplasm with uncertain malignant potential arising in the heterotopic adrenal cortex located in the liver of a patient with BWS.
Adrenal Cortex ; Adrenal Gland Neoplasms ; Beckwith-Wiedemann Syndrome ; Chromosomes, Human, Pair 11 ; Hepatoblastoma ; Humans ; Immunohistochemistry ; Liver ; Macroglossia ; Uniparental Disomy

OBJECTIVETo identify the genetic cause for a 11-year-old Chinese boy with Meier-Gorlin syndrome (MGS).

METHODSChromosomal microarray analysis (CMA) was used to detect potential variations, while whole exome sequencing (WES) was used to identify sequence variants. Sanger sequencing was used to confirm the suspected variants.

RESULTSThe boy has featured short stature, microtia, small patella, slender body build, craniofacial anomalies, and small testes with normal gonadotropin. A complete uniparental disomy of chromosome 16 was revealed by CMA. WES has identified a novel homozygous mutation c.67A>G (p.Lys23Glu) in ORC6 gene mapped to chromosome 16. As predicted by Alamut functional software, the mutation may affect the function of structural domain of the ORC6 protein.

CONCLUSIONThe patient is probably the first diagnosed MGS case in China, who carried a novel homozygous mutation of the ORC6 gene and uniparental disomy of chromosome 16. The effect of this novel mutation on the growth and development needs to be further investigated.

Base Sequence ; Child ; Chromosomes, Human, Pair 16 ; genetics ; Congenital Microtia ; genetics ; Family Health ; Fathers ; Growth Disorders ; genetics ; Heterozygote ; Humans ; Male ; Micrognathism ; genetics ; Mutation ; Origin Recognition Complex ; genetics ; Patella ; abnormalities ; Polymerase Chain Reaction ; methods ; Sequence Analysis, DNA ; methods ; Uniparental Disomy ; genetics

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.
Alleles ; Chromosomes, Human, Pair 22* ; Comparative Genomic Hybridization ; Exons ; Founder Effect ; Haplotypes ; Humans ; Leukoencephalopathies* ; Loss of Heterozygosity ; Megalencephaly ; Mothers ; Seizures ; Uniparental Disomy*

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.
Chromosome Aberrations ; Chromosomes, Human, Pair 20* ; Constitution and Bylaws ; Fetus ; Mosaicism ; Placenta ; Pregnancy, High-Risk* ; Trisomy ; Uniparental Disomy*

Pseudohypoparathyroidism type 1b (PHP 1b) is the result of end organ resistance to parathyroid hormone (PTH) in the absence of any features of Albright's hereditary osteodystrophy. There are two subtypes of PHP 1b with different genetic mechanisms. One subtype is related to a maternally derived 3kb microdeletion involving STX 16 gene, and is inherited in an autosomal dominant mode. Familial autosomal dominant inheritance of PHP 1b is relatively rare. The other subtype is associated with more extensive loss of imprinting at the GNAS locus that affects at least one additional differential methylated (hypermethylation at neuroendocrine secretory protein and hypomethylation at antisense transcript and or extra-large stimulatory G protein region) without microdeletion of the STX 16 or AS gene. It can be sporadic due to an imprinting defect in the GNAS gene. In our case, an 8-year-old girl was referred for suspected PHP with no feature of Albright hereditary osteodystrophy. Blood test results revealed hypocalcemia and hyperphosphatemia. Elevated PTH was also checked. There was no family history of endocrine or developmental problem. Her intelligence was normal, but she had inferior sociability at that time. Based on above, we diagnosed a rare case of paternal uniparental disomy of the long arm of chromosome 20 as the cause of PHP 1b by microsatellite marker test of chromosome 20.
Arm ; Child ; Chromosomes, Human, Pair 20 ; Female ; GTP-Binding Proteins ; Hematologic Tests ; Humans ; Hyperphosphatemia ; Hypocalcemia ; Intelligence ; Microsatellite Repeats ; Parathyroid Hormone ; Pseudohypoparathyroidism* ; Uniparental Disomy* ; Wills