De Novo Frameshift Variants in the Neuronal Splicing Factor NOVA2 Result in a Common C-Terminal Extension and Cause a Severe Form of Neurodevelopmental Disorder.

The neuro-oncological ventral antigen 2 (NOVA2) protein is a major factor regulating neuron-specific alternative splicing (AS), previously associated with an acquired neurologic condition, the paraneoplastic opsoclonus-myoclonus ataxia (POMA). We report here six individuals with de novo frameshift variants in NOVA2 affected with a severe neurodevelopmental disorder characterized by intellectual disability (ID), motor and speech delay, autistic features, hypotonia, feeding difficulties, spasticity or ataxic gait, and abnormal brain MRI. The six variants lead to the same reading frame, adding a common proline rich C-terminal part instead of the last KH RNA binding domain. We detected 41 genes differentially spliced after NOVA2 downregulation in human neural cells. The NOVA2 variant protein shows decreased ability to bind target RNA sequences and to regulate target AS events. It also fails to complement the effect on neurite outgrowth induced by NOVA2 downregulation in vitro and to rescue alterations of retinotectal axonal pathfinding induced by loss of NOVA2 ortholog in zebrafish. Our results suggest a partial loss-of-function mechanism rather than a full heterozygous loss-of-function, although a specific contribution of the novel C-terminal extension cannot be excluded.

Turner syndrome due to Xp22.33 deletion with preserved gonadal function: case report.

Turner syndrome (TS) is a chromosomal condition affecting 1 in 2000 females characterized by partial or complete loss of one of the X chromosomes. We describe an 11-year-old female who was recently diagnosed with TS. Karyotype revealed a deletion of the distal portion of chromosome X. Chromosome single nucleotide polymorphism (SNP) array revealed microdeletion of Xp22.33p22.12. Patient reached her menarche at age 11 years. Both the patient and her mother have short stature. Her mother, however, has a normal karyotype. This is one of few case reports of TS with microdeletion of Xp22.33 reported in the literature, with normal ovarian function and possible future transmission of the deletion to the next generations.

A unique association of Noonan syndrome and 47,XYY syndrome in a male presenting with failure to thrive.

We describe a 24-month-old male patient who presented to our Genetics-Endocrinology Clinic with a history of failure to thrive, short stature and cryptorchidism. Soon after birth he was diagnosed with 47,XYY syndrome, but due unusual facial features had further diagnostic workup which revealed Noonan syndrome (NS) as well. This report illustrates significant phenotypic-cytogenetic variability within the clinical presentation of NS and 47,XYY syndrome, as well as the need to investigate patients for other genetic defects when phenotype does not correlate with genotype. Furthermore, in this case, the cellular pathways attenuating growth via PTPN11 mutation appear to supersede the SHOX overdosage-an observation that can lead to further research in genetic mechanisms of growth physiology.

Anterior Pituitary Aplasia in an Infant with Ring Chromosome 18p Deletion.

We present the first reported case of an infant with 18p deletion syndrome with anterior pituitary aplasia secondary to a ring chromosome. Endocrine workup soon after birth was reassuring; however, repeat testing months later confirmed central hypopituitarism. While MRI reading initially indicated no midline defects, subsequent review of the images confirmed anterior pituitary aplasia with ectopic posterior pituitary. This case demonstrates how deletion of genetic material, even if resulting in a chromosomal ring, still results in a severe syndromic phenotype. Furthermore, it demonstrates the necessity of close follow-up in the first year of life for children with 18p deletion syndrome and emphasizes the need to verify radiology impressions if there is any doubt as to the radiologic findings.