Recessive mutations in the cartilage-associated protein (CRTAP), leucine proline-enriched proteoglycan 1 (LEPRE1) and peptidyl prolyl cis-trans isomerase B (PPIB) genes result in phenotypes that range from lethal in the perinatal period to severe deforming osteogenesis imperfecta (OI). These genes encode CRTAP (encoded by CRTAP), prolyl 3-hydroxylase 1 (P3H1; encoded by LEPRE1) and cyclophilin B (CYPB; encoded by PPIB), which reside in the rough endoplasmic reticulum (RER) and can form a complex involved in prolyl 3-hydroxylation in type I procollagen. CYPB, a prolyl cis-trans isomerase, has been thought to drive the prolyl-containing peptide bonds to the trans configuration needed for triple helix formation. Here, we describe mutations in PPIB identified in cells from three individuals with OI. Cultured dermal fibroblasts from the most severely affected infant make some overmodified type I procollagen molecules. Proα1(I) chains are slow to assemble into trimers, and abnormal procollagen molecules concentrate in the RER, and bind to protein disulfide isomerase (PDI) and prolyl 4-hydroxylase 1 (P4H1). These findings suggest that although CYPB plays a role in helix formation another effect is on folding of the C-terminal propeptide and trimer formation. The extent of procollagen accumulation and PDI/P4H1 binding differs among cells with mutations in PPIB, CRTAP and LEPRE1 with the greatest amount in PPIB-deficient cells and the least in LEPRE1-deficient cells. These findings suggest that prolyl cis-trans isomerase may be required to effectively fold the proline-rich regions of the C-terminal propeptide to allow proα chain association and suggest an order of action for CRTAP, P3H1 and CYPB in procollagen biosynthesis and pathogenesis of OI.

Newborn screening (NBS) programs have been successful in identifying infants with rare, treatable, congenital conditions. While current programs rely largely on biochemical analysis, some predict that in the future, genome sequencing may be used as an adjunct. The purpose of this exploratory pilot study was to begin to characterize genetics professionals' opinions of the use of whole-genome sequencing (WGS) in NBS. We surveyed members of the American College of Medical Genetics and Genomics (ACMG) via an electronic survey distributed through email. The survey included questions about results disclosure, the current NBS paradigm, and the current criteria for adding a condition to the screening panel. The response rate was 7.3 % (n = 113/1549). The majority of respondents (85 %, n = 96/113) felt that WGS should not be currently used in NBS, and that if it were used, it should not be mandatory (86.5 %, n = 96/111). However, 75.7 % (n = 84/111) foresee it as a future use of WGS. Respondents felt that accurate interpretation of results (86.5 %, n = 83/96), a more extensive consent process (72.6 %, n = 69/95), pre- (79.2 %, n = 76/96) and post-test (91.6 %, n = 87/95) counseling, and comparable costs (70.8 %, n = 68/96) and turn-around-times (64.6 %, n = 62/96) to current NBS would be important for using WGS in NBS. Participants were in favor of disclosing most types of results at some point in the lifetime. However, the majority (87.3 %, n = 96/110) also indicated that parents should be able to choose what results are disclosed. Overall, respondents foresee NBS as a future use of WGS, but indicated that WGS should not occur within the framework of traditional NBS. They agreed with the current criteria for including a condition on the recommended uniform screening panel (RUSP). Further discussion about these criteria is needed in order to better understand how they could be utilized if WGS is incorporated into NBS.

Background Disease severity is important when considering genes for inclusion on reproductive expanded carrier screening (ECS) panels. We applied a validated and previously published algorithm that classifies diseases into four severity categories (mild, moderate, severe, and profound) to 176 genes screened by ECS. Disease traits defining severity categories in the algorithm were then mapped to four severity‐related ECS panel design criteria cited by the American College of Obstetricians and Gynecologists (ACOG). Methods Eight genetic counselors (GCs) and four medical geneticists (MDs) applied the severity algorithm to subsets of 176 genes. MDs and GCs then determined by group consensus how each of these disease traits mapped to ACOG severity criteria, enabling determination of the number of ACOG severity criteria met by each gene. Results Upon consensus GC and MD application of the severity algorithm, 68 (39%) genes were classified as profound, 71 (40%) as severe, 36 (20%) as moderate, and one (1%) as mild. After mapping of disease traits to ACOG severity criteria, 170 out of 176 genes (96.6%) were found to meet at least one of the four criteria, 129 genes (73.3%) met at least two, 73 genes (41.5%) met at least three, and 17 genes (9.7%) met all four. Conclusion This study classified the severity of a large set of Mendelian genes by collaborative clinical expert application of a trait‐based algorithm. Further, it operationalized difficult to interpret ACOG severity criteria via mapping of disease traits, thereby promoting consistency of ACOG criteria interpretation.

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.