YWHAE loss of function causes a rare neurodevelopmental disease with brain abnormalities in human and mouse

PURPOSE

Miller-Dieker syndrome is caused by a multiple-gene deletion, including PAFAH1B1 and YWHAE. While deletion of PAFAH1B1 causes lissencephaly unambiguously, deletion of YWHAE alone has not clearly been linked to a human disorder.

METHODS

Cases with YWHAE variants were collected through international data-sharing networks. To address the specific impact of YWHAE loss of function, we phenotyped a mouse knockout of Ywhae.

RESULTS

We report a series of 10 individuals with heterozygous loss-of-function YWHAE variants (3 SNVs, 7 deletions <1 Mb encompassing YWHAE but not PAFAH1B1), including 8 new cases and 2 follow-ups, added with 5 cases (CNVs) from literature review. While, until now, only one intragenic deletion has been described in YWHAE, we report 4 new variants specifically in YWHAE (3 splice variants and 1 intragenic deletion). The most frequent manifestations are developmental delay, delayed speech, seizures and brain malformations including corpus callosum hypoplasia, delayed myelination, ventricular dilatation. Individuals with variants affecting YWHAE alone have milder features than those with larger deletions. Neuroanatomical studies in Ywhae^-/- mice revealed brain structural defects including thin cerebral cortex, corpus callosum dysgenesis, hydrocephalus paralleling those seen in humans.

CONCLUSION

This study further demonstrates that YWHAE loss-of-function variants cause a neurodevelopmental disease with brain abnormalities.

Genomic and phenotypic characterization of 404 individuals with neurodevelopmental disorders caused by CTNNB1 variants

PURPOSE

Germline loss-of-function variants in CTNNB1 cause neurodevelopmental disorder with spastic diplegia and visual defects (NEDSDV; OMIM 615075) and are the most frequent, recurrent monogenic cause of cerebral palsy (CP). We investigated the range of clinical phenotypes owing to disruptions of CTNNB1 to determine the association between NEDSDV and CP.

METHODS

Genetic information from 404 individuals with collectively 392 pathogenic CTNNB1 variants were ascertained for the study. From these, detailed phenotypes for 52 previously unpublished individuals were collected and combined with 68 previously published individuals with comparable clinical information. The functional effects of selected CTNNB1 missense variants were assessed using TOPFlash assay.

RESULTS

The phenotypes associated with pathogenic CTNNB1 variants were similar. A diagnosis of CP was not significantly associated with any set of traits that defined a specific phenotypic subgroup, indicating that CP is not additional to NEDSDV. Two CTNNB1 missense variants were dominant negative regulators of WNT signaling, highlighting the utility of the TOPFlash assay to functionally assess variants.

CONCLUSION

NEDSDV is a clinically homogeneous disorder irrespective of initial clinical diagnoses, including CP, or entry points for genetic testing.

Next-Generation Sequencing Screening of 43 Families with Non-Syndromic Early-Onset High Myopia: A Clinical and Genetic Study

Early-onset high myopia (EoHM) is a disease that causes a spherical refraction error of ≥-6 diopters before 10 years of age, with potential multiple ocular complications. In this article, we report a clinical and genetic study of 43 families with EoHM recruited in our center. A complete ophthalmological evaluation was performed, and a sample of peripheral blood was obtained from proband and family members. DNA was analyzed using a customized next-generation sequencing panel that included 419 genes related to ophthalmological disorders with a suspected genetic cause, and genes related to EoHM pathogenesis. We detected pathogenic and likely pathogenic variants in 23.9% of the families and detected variants of unknown significance in 76.1%. Of these, 5.7% were found in genes related to non-syndromic EoHM, 48.6% in genes associated with inherited retinal dystrophies that can include a syndromic phenotype, and 45.7% in genes that are not directly related to EoHM or retinal dystrophy. We found no candidate genes in 23% of the patients, which suggests that further studies are needed. We propose a systematic genetic analysis for patients with EoHM because it helps with follow-up, prognosis and genetic counseling.

The clinical and molecular spectrum of QRICH1 associated neurodevelopmental disorder

De novo variants in QRICH1 (Glutamine-rich protein 1) has recently been reported in 11 individuals with intellectual disability (ID). The function of QRICH1 is largely unknown but it is likely to play a key role in the unfolded response of endoplasmic reticulum stress through transcriptional control of proteostasis. In this study, we present 27 additional individuals and delineate the clinical and molecular spectrum of the individuals (n = 38) with QRICH1 variants. The main clinical features were mild to moderate developmental delay/ID (71%), nonspecific facial dysmorphism (92%) and hypotonia (39%). Additional findings included poor weight gain (29%), short stature (29%), autism spectrum disorder (29%), seizures (24%) and scoliosis (18%). Minor structural brain abnormalities were reported in 52% of the individuals with brain imaging. Truncating or splice variants were found in 28 individuals and 10 had missense variants. Four variants were inherited from mildly affected parents. This study confirms that heterozygous QRICH1 variants cause a neurodevelopmental disorder including short stature and expands the phenotypic spectrum to include poor weight gain, scoliosis, hypotonia, minor structural brain anomalies, and seizures. Inherited variants from mildly affected parents are reported for the first time, suggesting variable expressivity.

ZTTK syndrome: Clinical and molecular findings of 15 cases and a review of the literature

Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome is caused by de novo loss-of-function variants in the SON gene (MIM #617140). This multisystemic disorder is characterized by intellectual disability, seizures, abnormal brain imaging, variable dysmorphic features, and various congenital anomalies. The wide application and increasing accessibility of whole exome sequencing (WES) has helped to identify new cases of ZTTK syndrome over the last few years. To date, there have been approximately 45 cases reported in the literature. Here, we describe 15 additional individuals with variants in the SON gene, including those with missense variants bringing the total number of known cases to 60. We have reviewed the clinical and molecular data of these new cases and all previously reported cases to further delineate the most common as well as emerging clinical findings related to this syndrome. Furthermore, we aim to delineate any genotype-phenotype correlations specifically for a recurring pathogenic four base pair deletion (c.5753_5756del) along with discussing the impact of missense variants seen in the SON gene.

Schuurs-Hoeijmakers Syndrome (PACS1 Neurodevelopmental Disorder): Seven Novel Patients and a Review

Schuurs–Hoeijmakers syndrome (SHMS) or PACS1 Neurodevelopmental disorder is a rare disorder characterized by intellectual disability, abnormal craniofacial features and congenital malformations. SHMS is an autosomal dominant hereditary disease caused by pathogenic variants in the PACS1 gene. PACS1 is a trans-Golgi-membrane traffic regulator that directs protein cargo and several viral envelope proteins. It is upregulated during human embryonic brain development and has low expression after birth. So far, only 54 patients with SHMS have been reported. In this work, we report on seven new identified SHMS individuals with the classical c.607C > T: p.Arg206Trp PACS1 pathogenic variant and review clinical and molecular aspects of all the patients reported in the literature, providing a summary of clinical findings grouped as very frequent (≥75% of patients), frequent (50–74%), infrequent (26–49%) and rare (less than ≤25%).