Case Report: An Adult Case of Poretti-Boltshauser Syndrome Diagnosed by Medical Checkup.

This report describes an adult case of Poretti-Boltshauser syndrome (PTBHS) and with novel variants of LAMA1. A 65-year-old Japanese woman with cerebellar malformation identified during a medical checkup was referred to our hospital. Subsequently, neurological examination, brain imaging, and genetic investigation via whole-exome sequencing were performed. The patient presented with mild cerebellar ataxia and intellectual disability. Magnetic resonance imaging revealed cerebellar dysplasia and cysts and an absence of molar tooth sign. Genetic analysis revealed a novel homozygous variant of c.1711_1712del in LAMA1 (NM_005559.4). Most cases with PTBHS are reported in pediatric patients; however, our patient expressed a mild phenotype and was undiagnosed until her 60 s. These findings suggest that PTBHS should be considered in not only pediatric cerebellar dysplasia but also adult cerebellar ataxia with mild presentation.

Biallelic CC2D2A variants, SNV and LINE-1 insertion simultaneously identified in siblings using long-read whole-genome sequencing and haplotype phasing.

Joubert syndrome (JBTS) is characterized by a magnetic resonance imaging appearance called 'molar tooth sign', neonatal breathing dysregulation and hypotonia, and developmental delay. Whole-exome analysis based on short-read sequencing has often contributed to the identification of causative single-nucleotide variants in patients clinically diagnosed with JBTS. However, ~10% of them are still undiagnosed even though a single possible pathogenic variant has been identified. We report a successful identification of biallelic variants using long-read whole-genome sequencing and haplotype phasing analysis in a family with two Japanese siblings having morphological brain abnormalities. The affected siblings had a novel nonsynonymous variant (CC2D2A:NM_001080522.2:c.4454A>G:p.(Tyr1485Cys)) and an exonic insertion of Long INterspercsed Element-1 (LINE-1). The allelicity of these variants was clearly proven without the data of parents. Finally, our survey of in-house genome sequencing data indicates that there are rare carriers of CC2D2A related diseases, who harbour the exonic LINE-1 insertion in the CC2D2A gene.

Four pedigrees with aminoacyl-tRNA synthetase abnormalities.

Aminoacyl tRNA synthetases (ARSs) are highly conserved enzymes that link amino acids to their cognate tRNAs. Thirty-seven ARSs are known and their deficiencies cause various genetic disorders. Variants in some ARSs are associated with the autosomal dominant inherited form of axonal neuropathy, including Charcot-Marie-Tooth (CMT) disease. Variants of genes encoding ARSs often cause disorders in an autosomal recessive fashion. The clinical features of cytosolic ARS deficiencies are more variable, including systemic features. Deficiencies of ARSs localized in the mitochondria are often associated with neurological disorders including Leigh and early-onset epileptic syndromes. Whole exome sequencing (WES) is an efficient way to identify the genes causing various symptoms in patients. We identified 4 pedigrees with novel compound heterozygous variants in ARS genes (WARS1, MARS1, AARS2, and PARS2) by WES. Some unique manifestations were noted. The number of patients with ARSs has been increasing since the application of WES. Our findings broaden the known genetic and clinical spectrum associated with ARS variants.

A novel missense variant of the GNAI3 gene and recognisable morphological characteristics of the mandibula in ARCND1.

Auriculocondylar syndrome (ARCND) is an autosomal monogenic disorder characterised by external ear abnormalities and micrognathia due to hypoplasia of the mandibular rami, condyle and coronoid process. Genetically, three subtypes of ARCND (ARCND1, ARCND2 and ARCND3) have been reported. To date, five pathogenic variants of GNAI3 have been reported in ARCND1 patients. Here, we report a novel variant of GNAI3 (NM_006496:c.807C>A:p.(Asn269Lys)) in a Japanese girl with micrognathia using trio-based whole exome sequencing analysis. The GNAI3 gene encodes a heterotrimeric guanine nucleotide-binding protein. The novel variant locates the guanine nucleotide-binding site, and the substitution was predicted to interfere with guanine nucleotide-binding by in silico structural analysis. Three-dimensional computer tomography scan, or cephalogram, displayed severely hypoplastic mandibular rami and fusion to the medial and lateral pterygoid plates, which have been recognised in other ARCND1 patients, but have not been described in ARCND2 and ARCND3, suggesting that these may be distinguishable features in ARCND1.

Blended phenotype of combination of HERC2 and AP3B2 deficiency and Angelman syndrome caused by paternal isodisomy of chromosome 15.

Angelman syndrome is a neurodevelopmental disorder characterized by intellectual disability (ID), a distinctive gait pattern, abnormal behaviors, severe impairment in language development, and characteristic facial features. Most cases are caused by the absence of a maternal contribution to the imprinted region on chromosome 15q11-q13. Here, we present the first reported case of a 3-year-old boy with an atypical phenotype of Angelman syndrome due to uniparental isodisomy with two recessive homozygous pathogenic variants: in HERC2 and AP3B2. Known phenotypes related to HERC2 and AP3B2 include ID and early infantile epileptic encephalopathy, respectively. The patient had severe global developmental delay and profound ID and showed a happy demeanor, stereotypic laughter, and hand-flapping movements, but also irritability. Craniofacial dysmorphic features, including brachycephaly, strabismus, wide ala nasi, short philtrum, wide open mouth, and slight hypopigmentation were seen. Progressive microcephaly was noted. Magnetic resonance imaging of the brain showed delayed myelination and cerebral atrophy. Trio whole exome sequencing and CGH-SNP array analysis revealed paternal uniparental isodisomy of chromosome 15 and two coexisting recessive diseases resulting from homozygous HERC2 and AP3B2 pathogenic variants. The pathogenic variant in HERC2 was inherited from his heterozygous-carrier father, and the variant in AP3B2 was de novo. We suppose that these unusual features were the combination of the effect of three concomitant disorders.

Definitive diagnosis of mandibular hypoplasia, deafness, progeroid features and lipodystrophy (MDPL) syndrome caused by a recurrent de novo mutation in the POLD1 gene.

Segmental progeroid syndromes with lipodystrophy are extremely rare, heterogeneous, and complex multi-system disorders that are characterized by phenotypic features of premature aging affecting various tissues and organs. In this study, we present a "sporadic/isolated" Japanese woman who was ultimately diagnosed with mandibular hypoplasia, deafness, progeroid features, and progressive lipodystrophy (MDPL) syndrome (MIM #615381) using whole exome sequencing analysis. She had been suspected as having atypical Werner syndrome and/or progeroid syndrome based on observations spanning a 30-year period; however, repeated genetic testing by Sanger sequencing did not identify any causative mutation related to various subtypes of congenital partial lipodystrophy (CPLD) and/or mandibular dysplasia with lipodystrophy (MAD). Recently, MDPL syndrome has been described as a new entity showing progressive lipodystrophy. Furthermore, polymerase delta 1 (POLD1) gene mutations on chromosome 19 have been identified in patients with MDPL syndrome. To date, 21 cases with POLD1-related MDPL syndrome have been reported worldwide, albeit almost entirely of European origin. Here, we identified a de novo mutation in exon 15 (p.Ser605del) of the POLD1 gene in a Japanese case by whole exome sequencing. To the best of our knowledge, this is the first identified case of MDPL syndrome in Japan. Our results provide further evidence that mutations in POLD1 are responsible for MDPL syndrome and serve as a common genetic determinant across different ethnicities.

Functional analysis of RRAS2 pathogenic variants with a Noonan-like phenotype.

Introduction: RRAS2, a member of the R-Ras subfamily of Ras-like low-molecular-weight GTPases, is considered to regulate cell proliferation and differentiation via the RAS/MAPK signaling pathway. Seven RRAS2 pathogenic variants have been reported in patients with Noonan syndrome; however, few functional analyses have been conducted. Herein, we report two patients who presented with a Noonan-like phenotype with recurrent and novel RRAS2 pathogenic variants (p.Gly23Val and p.Gly24Glu, respectively) and the results of their functional analysis. Materials and methods: Wild-type (WT) and mutant RRAS2 genes were transiently expressed in Human Embryonic Kidney293 cells. Expression of RRAS2 and phosphorylation of ERK1/2 were confirmed by Western blotting, and the RAS signaling pathway activity was measured using a reporter assay system with the serum response element-luciferase construct. WT and p.Gly23Val RRAS2 were expressed in Drosophila eye using the glass multiple reporter-Gal4 driver. Mutant mRNA microinjection into zebrafish embryos was performed, and the embryo jaws were observed. Results: No obvious differences in the expression of proteins WT, p.Gly23Val, and p.Gly24Glu were observed. The luciferase reporter assay showed that the activity of p.Gly23Val was 2.45 ± 0.95-fold higher than WT, and p.Gly24Glu was 3.06 ± 1.35-fold higher than WT. For transgenic flies, the p.Gly23Val expression resulted in no adults flies emerging, indicating lethality. For mutant mRNA-injected zebrafish embryos, an oval shape and delayed jaw development were observed compared with WT mRNA-injected embryos. These indicated hyperactivity of the RAS signaling pathway. Discussion: Recurrent and novel RRAS2 variants that we reported showed increased in vitro or in vivo RAS signaling pathway activity because of gain-of-function RRAS2 variants. Clinical features are similar to those previously reported, suggesting that RRAS2 gain-of-function variants cause this disease in patients.