Frequency of Sex Chromosome Involvement in a Large Cohort of Subjects with Two Copy Number Variants

Copy number variants (CNVs) are a common finding in the clinical setting and contribute to both genetic variation and disease. Studies have described the accumulation of multiple CNVs as a disease-modifying mechanism. While it has been described how additional CNVs may play a role in phenotype, in which ways and to what extent sex chromosomes are involved in dual CNV scenario has not been fully defined. To describe the distribution of CNVs, a secondary data analysis using the DECIPHER database on 2,273 de-identified individuals with two CNVs was performed. CNVs were designated larger and secondary based on size and characteristics. We found that the X chromosome was observed to be the most common chromosome involved in secondary CNVs. Further analysis showed CNVs on the sex chromosome have significant differences compared to autosomes when comparing median size (p = 0.013), pathogenicity groups (p < 0.001), and variant classification (p = 0.001). Lastly, we identified chromosome combinations for larger and secondary CNVs and observed the plurality of secondary CNVs fell in the same chromosome as the larger. The observations of this study provide additional information on sex chromosome CNV involvement in a variety of indications.

Human KCNQ5 de novo mutations underlie epilepsy and intellectual disability

We identified six novel de novo human KCNQ5 variants in children with motor/language delay, intellectual disability (ID), and/or epilepsy by whole exome sequencing. These variants, comprising two nonsense and four missense alterations, were functionally characterized by electrophysiology in HEK293/CHO cells, together with four previously reported KCNQ5 missense variants (Lehman A, Thouta S, Mancini GM, Naidu S, van Slegtenhorst M, McWalter K, Person R, Mwenifumbo J, Salvarinova R; CAUSES Study; EPGEN Study; Guella I, McKenzie MB, Datta A, Connolly MB, Kalkhoran SM, Poburko D, Friedman JM, Farrer MJ, Demos M, Desai S, Claydon T. Am J Hum Genet 101: 65-74, 2017). Surprisingly, all eight missense variants resulted in gain of function (GOF) due to hyperpolarized voltage dependence of activation or slowed deactivation kinetics, whereas the two nonsense variants were confirmed to be loss of function (LOF). One severe GOF allele (P369T) was tested and found to extend a dominant GOF effect to heteromeric KCNQ5/3 channels. Clinical presentations were associated with altered KCNQ5 channel gating: milder presentations with LOF or smaller GOF shifts in voltage dependence [change in voltage at half-maximal conduction (ΔV₅₀) = ∼-15 mV] and severe presentations with larger GOF shifts in voltage dependence (ΔV₅₀ = ∼-30 mV). To examine LOF pathogenicity, two Kcnq5 LOF mouse lines were created with CRISPR/Cas9. Both lines exhibited handling- and thermal-induced seizures and abnormal cortical EEGs consistent with epileptiform activity. Our study thus provides evidence for in vivo KCNQ5 LOF pathogenicity and strengthens the contribution of both LOF and GOF mutations to global pediatric neurological impairment, including ID/epilepsy.NEW & NOTEWORTHY Six novel de novo human KCNQ5 variants were identified from children with neurodevelopmental delay, intellectual disability, and/or epilepsy. Expression of these variants along with four previously reported KCNQ5 variants from a similar cohort revealed GOF potassium channels, negatively shifted in V₅₀ of activation and/or delayed deactivation kinetics. GOF is extended to KCNQ5/3 heteromeric channels, making these the predominant channels affected in heterozygous de novo patients. Kcnq5 LOF mice exhibited seizures, consistent with in vivo pathogenicity.

Borealin directs recruitment of the CPC to oocyte chromosomes and movement to the microtubules

The chromosomes in the oocytes of many animals appear to promote bipolar spindle assembly. In Drosophila oocytes, spindle assembly requires the chromosome passenger complex (CPC), which consists of INCENP, Borealin, Survivin, and Aurora B. To determine what recruits the CPC to the chromosomes and its role in spindle assembly, we developed a strategy to manipulate the function and localization of INCENP, which is critical for recruiting the Aurora B kinase. We found that an interaction between Borealin and the chromatin is crucial for the recruitment of the CPC to the chromosomes and is sufficient to build kinetochores and recruit spindle microtubules. HP1 colocalizes with the CPC on the chromosomes and together they move to the spindle microtubules. We propose that the Borealin interaction with HP1 promotes the movement of the CPC from the chromosomes to the microtubules. In addition, within the central spindle, rather than at the centromeres, the CPC and HP1 are required for homologous chromosome bi-orientation.

The impact of genetic counseling on women's grief and coping following termination of pregnancy for fetal anomaly

Pregnancy termination for fetal anomaly (TFA) is a unique experience that can cause women to develop long-term complicated grief. Although a woman's experience with her healthcare providers has been previously identified as an important factor in coping, studies have shown that many women report their health care as lacking to some extent. Given the overlap in women's needs and the practice scope of a genetic counselor (GC), this study aimed to examine how genetic counseling may impact coping and explore women's expectations of GCs pre- and post-TFA. An online survey, which included the brief COPE and the short version of the Perinatal Grief Scale, was distributed among private online support groups. Appropriate statistical analysis tools, such as the Wilcoxon rank-sum and t test, were utilized for quantitative analysis of the 124 responses, and inductive content analysis was utilized for qualitative analysis. Of those who underwent TFA within the last two years, women who saw a GC utilized active coping, planning, and positive reframing significantly more than women who did not see a GC (p = 0.001, p = 0.031, p = 0.027, respectively). GCs were perceived to have a positive impact on coping when providing information, objective care, emotional support, support resources, and follow-up care; these practices encouraged confidence in their personal decision-making and gave women hope for the future. This study not only identified key counseling roles for GCs prior to a TFA, but also demonstrated that genetic counseling prior to TFA may be beneficial to coping. Further studies are warranted to explore the needs of a more diverse population and to identify appropriate genetic counseling training methods to support women pursuing TFA.

Examining genetic counselors' implicit attitudes toward disability

Genetic counselors have a unique role in healthcare that requires a balance between being a patient educator and patient advocate when discussing disability. This study aimed to determine genetic counselors' implicit attitudes toward disability, and identify what factors affect these implicit attitudes. Case scenarios involving disability were used to examine hypothetical estimates of time spent on different topics within a genetic counseling session. Implicit attitudes were measured using the validated Disability Attitudes Implicit Association Test (DA-IAT), and personal/professional experiences with disability were assessed. Analysis of 382 respondents of the electronic survey revealed that personal experience with individuals with disabilities was not significantly associated with implicit attitudes scores. In addition, results demonstrated that genetic counselors have a stronger bias toward ability (D_mean  = 0.62, D_std  = ±0.45) compared to previous participants of the DA-IAT (p < .005). Practice specialty, length of time in the genetic counseling field, or whether the participant was a practicing counselor or genetic counseling student were not associated with implicit attitudes scores. The bias toward ability observed across practice specialties may be due to shared factors that influence interest in this field, but may also potentially reflect the inability of the DA-IAT to capture the complexity of genetic counselors' relationship to individuals with disability. This study emphasizes the importance of incorporating patients' individual definitions of disability into genetic counseling sessions and building an environment of patient advocacy and education around their personal perspectives and needs.

Genetic Testing Practices of Genetic Counselors, Geneticists, and Pediatric Neurologists With Regard to Childhood-Onset Neurogenetic Conditions

Identifying genetic diagnoses for neurologic conditions with a considerable hereditary component, such as autism spectrum disorder, intellectual disability, and epilepsy, is critical to providing proper medical management for patients and their families. However, many patients with these conditions are not tested appropriately or receive no genetic testing at all. The current study was designed to characterize the genetic testing practices of the providers most likely to evaluate or order genetic testing for these patients: pediatric neurologists, geneticists, and genetic counselors. Significant variance was present between testing strategies selected by pediatric neurologists and those by geneticists and genetic counselors, supporting the need for updated genetic testing guidelines that are consistent across specialties. Pediatric neurologists also report lower confidence in ordering genetic testing and desire further education regarding genetic testing. Together, these results propose that continued integration of genetics providers, such as genetic counselors, into pediatric neurology clinics may improve utilization of genetic testing while reducing the burden on pediatric neurologists.

A De novo HDAC2 variant in a patient with features consistent with Cornelia de Lange syndrome phenotype

Cornelia de Lange syndrome (CdLS) is an autosomal dominant genetic disorder caused by pathogenic variants in NIPBL, RAD21, SMC3, HDAC8, or SMC1A; all of which code for proteins that are components of, or interact with, the cohesin complex. Despite the identification of multiple genes associated with CdLS, over 25% of individuals strongly suspected to have CdLS have negative genetic testing, indicating that there are additional genes associated with the condition. HDAC2 codes for histone deacetylase 2 (HDAC2) and, like HDAC8, is a Class 1 histone deacetylase. We present a patient with a novel de novo variant in HDAC2 with many clinical features consistent with CdLS including severe developmental delay, limb abnormalities, congenital heart defect, cryptorchidism and hypoplastic genitalia, growth retardation, and characteristic craniofacial features. Although variants in HDAC2 are not currently associated with human disease, the variant identified in this patient is within a highly conserved amino acid residue and has not been observed in healthy populations. This information, along with the patient's clinical presentation and the functional similarity between the HDAC2 and HDAC8 proteins, suggests that HDAC2 should be further investigated as a candidate gene for CdLS or a CdLS-like syndrome.