Noninvasive prenatal testing suggesting an abnormality in chromosome 15 confirmed to be a case of Prader-Willi syndrome caused by trisomy rescue in the neonatal period.

We report a case of a neonatal diagnosis of Prader-Willi syndrome caused by uniparental disomy. A 34-year-old pregnant woman underwent noninvasive prenatal testing (NIPT) in a hospital that was not certified by the Japanese Association of Medical Sciences. The results of trisomy 13, 18, and 21 were negative; however, a possible abnormality in chromosome 15 was indicated by the Z-score. Genetic counseling was not performed; thus, the woman did not understand the implication of this result. Therefore, she continued with the pregnancy and delivered a boy weighing 1892 g with hypogonadism at 38 weeks and 5 days. The infant was diagnosed with Prader-Willi syndrome caused by uniparental disomy derived from trisomy rescue. The NIPT results may have reflected placental mosaicism, emphasizing the importance of understanding the limitations of NIPT due to the presence of congenital chromosomal abnormalities that cannot be detected by NIPT platforms.

Genetic landscape of Rett syndrome-like phenotypes revealed by whole exome sequencing.

BACKGROUND: Rett syndrome (RTT) is a characteristic neurological disease presenting with regressive loss of neurodevelopmental milestones. Typical RTT is generally caused by abnormality of methyl-CpG binding protein 2 (MECP2). Our objective to investigate the genetic landscape of MECP2-negative typical/atypical RTT and RTT-like phenotypes using whole exome sequencing (WES). METHODS: We performed WES on 77 MECP2-negative patients either with typical RTT (n=11), atypical RTT (n=22) or RTT-like phenotypes (n=44) incompatible with the RTT criteria. RESULTS: Pathogenic or likely pathogenic single-nucleotide variants in 28 known genes were found in 39 of 77 (50.6%) patients. WES-based CNV analysis revealed pathogenic deletions involving six known genes (including MECP2) in 8 of 77 (10.4%) patients. Overall, diagnostic yield was 47 of 77 (61.0 %). Furthermore, strong candidate variants were found in four novel genes: a de novo variant in each of ATPase H+ transporting V0 subunit A1 (ATP6V0A1), ubiquitin-specific peptidase 8 (USP8) and microtubule-associated serine/threonine kinase 3 (MAST3), as well as biallelic variants in nuclear receptor corepressor 2 (NCOR2). CONCLUSIONS: Our study provides a new landscape including additional genetic variants contributing to RTT-like phenotypes, highlighting the importance of comprehensive genetic analysis.

Low-grade intraventricular hemorrhage disrupts cerebellar white matter in preterm infants: evidence from diffusion tensor imaging.

INTRODUCTION: Recent diffusion tensor imaging (DTI) studies have demonstrated that leakage of hemosiderin into cerebrospinal fluid (CSF), which is caused by high-grade intraventricular hemorrhage (IVH), can affect cerebellar development in preterm born infants. However, a direct effect of low-grade IVH on cerebellar development is unknown. Thus, we evaluated the cerebellar and cerebral white matter (WM) of preterm infants with low-grade IVH. METHODS: Using DTI tractography performed at term-equivalent age, we analyzed 42 infants who were born less than 30 weeks gestational age (GA) at birth (22 with low-grade IVH, 20 without). These infants were divided into two birth groups depending on GA, and we then compared the presence and absence of IVH which was diagnosed by cerebral ultrasound (CUS) within 10 days after birth or conventional magnetic resonance imaging (MRI) at term-equivalent age in each group. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) at the superior cerebellar peduncle (SCP), middle cerebellar peduncle (MCP), motor tract, and sensory tract were measured. RESULTS: In the SCP, preterm born infants with IVH had lower FA values compared with infants without IVH. In particular, younger preterm birth with IVH had lower FA values in the SCP and motor tract and higher ADC values in the MCP. CONCLUSION: Low-grade IVH impaired cerebellar and cerebral WM, especially in the SCP. Moreover, younger preterm infants exhibited greater disruptions to cerebellar WM and the motor tract than infants of older preterm birth.

Bilateral choroid plexus resection in a 9p hexasomy/tetrasomy mosaic patient.

Previous reports have shown that a gain of the chromosome 9 short arm (9p) is associated with choroid plexus hyperplasia (CPH). Furthermore, CPH can lead to communicating hydrocephalus; however, no cases of CPH with 9p gain requiring choroid plexus resection have been reported. Here, we describe the first case in which a 9p hexasomy/tetrasomy mosaic patient required choroid plexus resection for hydrocephalus. This finding suggested that the 9p copy number is correlated with CPH severity.

Effects of chemotherapy on the brain in childhood: diffusion tensor imaging of subtle white matter damage.

INTRODUCTION: With reducing mortality in children with hematological malignancies, the survivors' quality of life regarding development of chronic neurological disturbances is important. We aimed to determine whether chemotherapy affects white matter (WM). METHODS: Using brain diffusion tensor imaging, we evaluated 17 patients (15 with acute lymphoblastic leukemia, 2 with non-Hodgkin's lymphoma; 9 male, 8 female; age, 1.6-13 years) before and after chemotherapy. We measured the quantitative values of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) at the regions of interest (ROIs) such as periventricular WM, corona radiata, posterior limb of the internal capsule, and corpus callosum. We assessed sensorimotor and callosal tracts by tractography. RESULTS: Reduction in FA and increase in ADC were significant at the ROIs of the left and right anterior periventricular WM and corona radiata and at the tract passing through the genu. A significant reduction in FA with a nonsignificant increase in ADC was seen at the ROI of the genu and at the tracts passing through the body and isthmus. CONCLUSION: Chemotherapy in children with hematological malignancies predominantly affects the frontal WM. This finding might indicate a negative effect of chemotherapy on neurological development in children with hematological malignancies.

Regional Difference in Myelination in Monocarboxylate Transporter 8 Deficiency: Case Reports and Literature Review of Cases in Japan.

Background: Monocarboxylate transporter 8 (MCT8) is a thyroid hormone transmembrane transporter protein. MCT8 deficiency induces severe X-linked psychomotor retardation. Previous reports have documented delayed myelination in the central white matter (WM) in these patients; however, the regional pattern of myelination has not been fully elucidated. Here, we describe the regional evaluation of myelination in four patients with MCT8 deficiency. We also reviewed the myelination status of previously reported Japanese patients with MCT8 deficiency based on magnetic resonance imaging (MRI). Case Reports: Four patients were genetically diagnosed with MCT8 deficiency at the age of 4-9 months. In infancy, MRI signal of myelination was observed mainly in the cerebellar WM, posterior limb of internal capsule, and the optic radiation. There was progression of myelination with increase in age. Discussion: We identified 36 patients with MCT8 deficiency from 25 families reported from Japan. The available MRI images were obtained at the age of <2 years in 13 patients, between 2 and 4 years in six patients, between 4 and 6 years in three patients, and at ≥6 years in eight patients. Cerebellar WM, posterior limb of internal capsule, and optic radiation showed MRI signal of myelination by the age of 2 years, followed by centrum semiovale and corpus callosum by the age of 4 years. Most regions except for deep anterior WM showed MRI signal of myelination at the age of 6 years. Conclusion: The sequential pattern of myelination in patients with MCT8 deficiency was largely similar to that in normal children; however, delayed myelination of the deep anterior WM was a remarkable finding. Further studies are required to characterize the imaging features of patients with MCT8 deficiency.

High-fat diet accelerates extreme obesity with hyperphagia in female heterozygous Mecp2-null mice.

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutation of the methyl-CpG-binding protein 2 (MECP2) gene. Although RTT has been associated with obesity, the underlying mechanism has not yet been elucidated. In this study, female heterozygous Mecp2-null mice (Mecp2+/- mice), a model of RTT, were fed a normal chow diet or high-fat diet (HFD), and the changes in molecular signaling pathways were investigated. Specifically, we examined the expression of genes related to the hypothalamus and dopamine reward circuitry, which represent a central network of feeding behavior control. In particular, dopamine reward circuitry has been shown to regulate hedonic feeding behavior, and its disruption is associated with HFD-related changes in palatability. The Mecp2+/- mice that were fed the normal chow showed normal body weight and food consumption, whereas those fed the HFD showed extreme obesity with hyperphagia, an increase of body fat mass, glucose intolerance, and insulin resistance compared with wild-type mice fed the HFD (WT-HFD mice). The main cause of obesity in Mecp2+/--HFD mice was a remarkable increase in calorie intake, with no difference in oxygen consumption or locomotor activity. Agouti-related peptide mRNA and protein levels were increased, whereas proopiomelanocortin mRNA and protein levels were reduced in Mecp2+/--HFD mice with hyperleptinemia, which play an essential role in appetite and satiety in the hypothalamus. The conditioned place preference test revealed that Mecp2+/- mice preferred the HFD. Tyrosine hydroxylase and dopamine transporter mRNA levels in the ventral tegmental area, and dopamine receptor and dopamine- and cAMP-regulated phosphoprotein mRNA levels in the nucleus accumbens were significantly lower in Mecp2+/--HFD mice than those of WT-HFD mice. Thus, HFD feeding induced dysregulation of food intake in the hypothalamus and dopamine reward circuitry, and accelerated the development of extreme obesity associated with addiction-like eating behavior in Mecp2+/- mice.

Serial investigation of PTPN11 mutation in nonhematopoietic tissues in a patient with juvenile myelomonocytic leukemia who was treated with unrelated cord blood transplantation.

After allogeneic stem-cell transplantation, nonhematopoietic tissues contain donor-derived cells; however, whether cells from malignant hematological disease can also be found in nonhematopoietic tissues is unclear. This report describes a juvenile myelomonocytic leukemia (JMML) case with a typical PTPN11 mutation (p.E76K) at different allele frequencies in the bone marrow mononuclear cells, buccal smear cells, and fingernails at diagnosis, which was suggestive of PTPN11 somatic mosaicism; however, the PTPN11 mutation in the buccal smear cells and fingernails was lost after unrelated cord blood transplantation. These results suggest that JMML-derived cells may migrate into and reside in nonhematopoietic tissues and furthermore that these cells can be eradicated by cord blood transplantation.