Study of a fetus with confined placental mosaicism for trisomy 2 in conjunct with fetal uniparental disomy and a literature review / 中华医学遗传学杂志

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.

Clinical and genetic analysis of a child with maternal uniparental disomy of chromosome 20 / 中华医学遗传学杂志

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.

Clinical practice guidelines for the diagnosis of regions of homozygosity and uniparental disomy / 中华医学遗传学杂志

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.

Clinical practice guidelines for the diagnosis of regions of homozygosity and uniparental disomy / 中华医学遗传学杂志

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.

Análisis de variación del número de copias y de patrones de metilación en la región 15q11-q13 / Variation analysis of the number of copies and methylene patterns in region 15q11-q13

La región q11-q13 del cromosoma 15 humano es proclive a sufrir alteraciones genéticas. Algunos genes de la región presentan expresión parental diferencial monoalélica, regulada por imprinting (EI). Errores en la regulación del EI, disomías uniparentales (DSU), así como también el cambio en el número de copias genómicas (CNV) producidos por sitios susceptibles de quiebre cromosómico (BP), producen alteraciones en esta región. Las enfermedades más frecuentes asociadas son el síndrome de Prader-Willi, el síndrome de Angelman y el síndrome de microduplicación 15q11-q13. En el presente trabajo analizamos la región 15q11-q13 por Methyl specific-multiplex ligation-dependent probe amplification (MS-MLPA) en 181 muestras de ADN derivadas a nuestro servicio de análisis genético molecular. En este trabajo mostramos que, de las 181 muestras, 39 presentaron alteraciones detectables por MS-MLPA. El 61.5% (24/39) de esas alteraciones detectadas fueron deleciones, el 5.1% (2/39) duplicaciones y el 33.3%(13/39) DSU/EI. Los CNV fueron 4 veces más frecuentes que las DSU/EI (OR = 4; IC 95%: 1.56-10.25) consistente con la literatura. Entre los CNV, dos casos atípicos permiten postular posibles sitios BP que no han sido informados en la literatura previamente.

Human chromosome 15q11-q13 region is prone to suffer genetic alterations. Some genes of this region have a differential monoallelic imprinting-regulated expression pattern. Defects in imprinting regulation (IE), uniparental disomy (UPD) or copy number variation (CNV) due to chromosomal breakpoints (BP) in 15q11-q13 region, are associated with several diseases. The most frequent are Prader-Willi syndrome, Angelman syndrome and 15q11-q13 microduplication syndrome. In this work, we analyzed DNA samples from 181 patients with phenotypes which were compatible with the above-mentioned diseases, using Methyl specific-multiplex ligation-dependent probe amplification (MS-MLPA). We show that, of the 181 samples, 39 presented alterations detectable by MS-MLPA. Of those alterations, 61.5% (24/39) were deletions, 5.1% (2/39) duplications and 33.3% (13/39) UPD/IE. The CNV cases were 4 times more frequent than UPD/IE (OR= 4; IC 95%: 1.56-10.25), consistent with the literature. Among the CNVs, two atypical cases allow to postulate new possible BP sites that have not been reported previously in the literature.

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.

Another small supernumerary marker chromosome derived from chromosome 9 in a Klinefelter patient / Otro cromosoma marcador supernumerario pequeño derivado del cromosoma 9 en un paciente con el síndrome de Klinefelter

Marker chromosomes are very rare in Klinefelter patients and phenotypic findings are related to the affected chromosomal region. The phenotypic effects of small supernumerary marker chromosomes (sSMC) range from multiple malformations/mental retardation to no effect (ie a normal phenotype). This wide spectrum of phenotypes is due to the origin, structure and gene content of the marker chromosome. The first Klinefelter case with sSMC 9 was published by Liehr et al in 2005. The present case was referred for chromosomal analysis because of dysmorphic features, speech delay and mild mental retardation. Conventional cytogenetic analysis revealed the 47 XXY karyotype in 17 metaphases and the 48 XXY + marker karyotype in eight metaphases. Fluorescence in situ hybridization (FISH) analysis to identify the marker chromosome was performed using the LSI p16 (9p21) Spectrum Orange/CEP 9 SpectrumGreen Probe (Vysis CDKN2A/CEP 9 FISH Probe) and partial trisomy 9 mosaicism was confirmed in this patient. To our knowledge, this is the second case of Klinefelter syndrome with a small supernumerary marker chromosome derived from chromosome 9.

Los cromosomas marcadores son muy raros en los pacientes de Klinefelter, y los hallazgos fenotípicos se relacionan con la región cromosomática afectada. Los efectos fenotípicos de los cromosomas marcadores supernumerarios pequeños (sSMC) van desde el retraso mental y las malformaciones múltiples hasta la ausencia total de efectos (es decir, un fenotipo normal). Este amplio espectro de fenotipos se debe al origen, estructura y contenido del gen del cromosoma marcador. El primer caso de síntoma Klinefelter con sSMC 9 fue publicado por Liehr et al en 2005. El caso presente fue remitido para análisis cromosomático debido a rasgos dismórficos, retraso del habla, y retardo mental ligero. El análisis citogenético convencional reveló el cariotipo 47 XXY en 17 metafases y el cariotipo marcador 48 XXY+ en ocho metafases. El análisis mediante hibridación fluorescente in situ (FISH) para identificar el cromosoma marcador se realizó usando la sonda LSI p16 (9p21) Spectrum Orange/CEP 9 SpectrumGreen Probe (Vysis CDKN2A/CEP 9 FISH Probe). Un mosaicismo de trisomía 9 parcial fue confirmado en este paciente. Hasta donde sabemos, éste es el segundo caso de síndrome de Klinefelter con un cromosoma marcador supernumerario pequeño derivado del cromosoma 9.