Narrowing the diagnostic gap: Genomes, episignatures, long-read sequencing, and health economic analyses in an exome-negative intellectual disability cohort.

PURPOSE: Genome sequencing (GS)-specific diagnostic rates in prospective tightly ascertained exome sequencing (ES)-negative intellectual disability (ID) cohorts have not been reported extensively. METHODS: ES, GS, epigenetic signatures, and long-read sequencing diagnoses were assessed in 74 trios with at least moderate ID. RESULTS: The ES diagnostic yield was 42 of 74 (57%). GS diagnoses were made in 9 of 32 (28%) ES-unresolved families. Repeated ES with a contemporary pipeline on the GS-diagnosed families identified 8 of 9 single-nucleotide variations/copy-number variations undetected in older ES, confirming a GS-unique diagnostic rate of 1 in 32 (3%). Episignatures contributed diagnostic information in 9% with GS corroboration in 1 of 32 (3%) and diagnostic clues in 2 of 32 (6%). A genetic etiology for ID was detected in 51 of 74 (69%) families. Twelve candidate disease genes were identified. Contemporary ES followed by GS cost US$4976 (95% CI: $3704; $6969) per diagnosis and first-line GS at a cost of $7062 (95% CI: $6210; $8475) per diagnosis. CONCLUSION: Performing GS only in ID trios would be cost equivalent to ES if GS were available at $2435, about a 60% reduction from current prices. This study demonstrates that first-line GS achieves higher diagnostic rate than contemporary ES but at a higher cost.

Genomic multidisciplinary teams: A model for navigating genetic mainstreaming and precision medicine.

AIM: Recent rapid advances in genomics are revolutionising patient diagnosis and management of genetic conditions. However, this has led to many challenges in service provision, education and upskilling requirements for non-genetics health-care professionals and remuneration for genomic testing. In Australia, Medicare funding with a Paediatric genomic testing item for patients with intellectual disability or syndromic features has attempted to address this latter issue. The Sydney Children's Hospitals Network - Westmead (SCHN-W) Clinical Genetics Department established Paediatric and Neurology genomic multidisciplinary team (MDT) meetings to address the Medicare-specified requirement for discussion with clinical genetics, and increasing genomic testing advice requests. METHODS: This SCHN-W genomic MDT was evaluated with two implementation science frameworks - the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) and GMIR - Genomic Medicine Integrative Research frameworks. Data from June 2020 to July 2022 were synthesised and evaluated, as well as process mapping of the MDT service. RESULTS: A total of 205 patients were discussed in 34 MDT meetings, facilitating 148 genomic tests, of which 73 were Medicare eligible. This was equivalent to 26% of SCHN-W genetics outpatient activity, and 13% of all Medicare-funded paediatric genomic testing in NSW. 39% of patients received a genetic diagnosis. CONCLUSION: The genomic MDT facilitated increased genomic testing at a tertiary paediatric centre and is an effective model for mainstreaming and facilitating precision medicine. However, significant implementation issues were identified including cost and sustainability, as well as the high level of resourcing that will be required to scale up this approach to other areas of medicine.

The health care and societal costs of inherited retinal diseases in Australia: a microsimulation modelling study.

OBJECTIVES: To estimate the health care and societal costs of inherited retinal diseases (IRDs) in Australia. DESIGN, SETTING, PARTICIPANTS: Microsimulation modelling study based on primary data - collected in interviews of people with IRDs who had ophthalmic or genetic consultations at the Children's Hospital at Westmead or the Save Sight Institute (both Sydney) during 1 January 2019 - 31 December 2020, and of their carers and spouses - and linked Medicare Benefits Schedule (MBS) and Pharmaceutical Benefits Schedule (PBS) data. MAIN OUTCOME MEASURES: Annual and lifetime costs for people with IRDs and for their carers and spouses, grouped by payer (Australian government, state governments, individuals, private health insurance) and type (health care costs; societal costs: social support, National Disability Insurance Scheme (NDIS), income and taxation, costs associated with caring for family members with IRDs); estimated annual national cost of IRDs. RESULTS: Ninety-four people (74 adults, 20 people under 18 years; 55 girls and women [59%]) and 30 carers completed study surveys (participation rate: adults, 66%; children, 66%; carers, 63%). Total estimated lifetime cost was $5.2 million per person with an IRD, of which 87% were societal and 13% health care costs. The three highest cost items were lost income for people with IRDs ($1.4 million), lost income for their carers and spouses ($1.1 million), and social spending by the Australian government (excluding NDIS expenses: $1.0 million). Annual costs were twice as high for people who were legally blind as for those with less impaired vision ($83 910 v $41 357 per person). The estimated total annual cost of IRDs in Australia was $781 million to $1.56 billion. CONCLUSION: As the societal costs associated with IRDs are much larger than the health care costs, both contributors should be considered when assessing the cost-effectiveness of interventions for people with IRDs. The increasing loss of income across life reflects the impact of IRDs on employment and career opportunities.

De Novo ZMYND8 variants result in an autosomal dominant neurodevelopmental disorder with cardiac malformations.

PURPOSE: ZMYND8 encodes a multidomain protein that serves as a central interactive hub for coordinating critical roles in transcription regulation, chromatin remodeling, regulation of super-enhancers, DNA damage response and tumor suppression. We delineate a novel neurocognitive disorder caused by variants in the ZMYND8 gene. METHODS: An international collaboration, exome sequencing, molecular modeling, yeast two-hybrid assays, analysis of available transcriptomic data and a knockdown Drosophila model were used to characterize the ZMYND8 variants. RESULTS: ZMYND8 variants were identified in 11 unrelated individuals; 10 occurred de novo and one suspected de novo; 2 were truncating, 9 were missense, of which one was recurrent. The disorder is characterized by intellectual disability with variable cardiovascular, ophthalmologic and minor skeletal anomalies. Missense variants in the PWWP domain of ZMYND8 abolish the interaction with Drebrin and missense variants in the MYND domain disrupt the interaction with GATAD2A. ZMYND8 is broadly expressed across cell types in all brain regions and shows highest expression in the early stages of brain development. Neuronal knockdown of the DrosophilaZMYND8 ortholog results in decreased habituation learning, consistent with a role in cognitive function. CONCLUSION: We present genomic and functional evidence for disruption of ZMYND8 as a novel etiology of syndromic intellectual disability.

Neurogenetic fetal akinesia and arthrogryposis: genetics, expanding genotype-phenotypes and functional genomics.

BACKGROUND: Fetal akinesia and arthrogryposis are clinically and genetically heterogeneous and have traditionally been refractive to genetic diagnosis. The widespread availability of affordable genome-wide sequencing has facilitated accurate genetic diagnosis and gene discovery in these conditions. METHODS: We performed next generation sequencing (NGS) in 190 probands with a diagnosis of arthrogryposis multiplex congenita, distal arthrogryposis, fetal akinesia deformation sequence or multiple pterygium syndrome. This sequencing was a combination of bespoke neurogenetic disease gene panels and whole exome sequencing. Only class 4 and 5 variants were reported, except for two cases where the identified variants of unknown significance (VUS) are most likely to be causative for the observed phenotype. Co-segregation studies and confirmation of variants identified by NGS were performed where possible. Functional genomics was performed as required. RESULTS: Of the 190 probands, 81 received an accurate genetic diagnosis. All except two of these cases harboured class 4 and/or 5 variants based on the American College of Medical Genetics and Genomics guidelines. We identified phenotypic expansions associated with CACNA1S, CHRNB1, GMPPB and STAC3. We describe a total of 50 novel variants, including a novel missense variant in the recently identified gene for arthrogryposis with brain malformations-SMPD4. CONCLUSIONS: Comprehensive gene panels give a diagnosis for a substantial proportion (42%) of fetal akinesia and arthrogryposis cases, even in an unselected cohort. Recently identified genes account for a relatively large proportion, 32%, of the diagnoses. Diagnostic-research collaboration was critical to the diagnosis and variant interpretation in many cases, facilitated genotype-phenotype expansions and reclassified VUS through functional genomics.

Paediatric genomic testing: Navigating genomic reports for the general paediatrician.

Monogenic rare disorders contribute significantly to paediatric morbidity and mortality, and elucidation of the underlying genetic cause may have benefits for patients, families and clinicians. Advances in genomic technology have enabled diagnostic yields of up to 50% in some paediatric cohorts. This has led to an increase in the uptake of genetic testing across paediatric disciplines. This can place an increased burden on paediatricians, who may now be responsible for interpreting and explaining test results to patients. However, genomic results can be complex, and sometimes inconclusive for the ordering paediatrician. Results may also cause uncertainty and anxiety for patients and their families. The paediatrician's genetic literacy and knowledge of genetic principles are therefore critical to inform discussions with families and guide ongoing patient care. Here, we present four hypothetical case vignettes where genomic testing is undertaken, and discuss possible results and their implications for paediatricians and families. We also provide a list of key terms for paediatricians.

Whole Genome Sequencing, Focused Assays and Functional Studies Increasing Understanding in Cryptic Inherited Retinal Dystrophies.

The inherited retinal dystrophies (IRDs) are a clinically and genetically complex group of disorders primarily affecting the rod and cone photoreceptors or other retinal neuronal layers, with emerging therapies heralding the need for accurate molecular diagnosis. Targeted capture and panel-based strategies examining the partial or full exome deliver molecular diagnoses in many IRD families tested. However, approximately one in three families remain unsolved and unable to obtain personalised recurrence risk or access to new clinical trials or therapy. In this study, we investigated whole genome sequencing (WGS), focused assays and functional studies to assist with unsolved IRD cases and facilitate integration of these approaches to a broad molecular diagnostic clinical service. The WGS approach identified variants not covered or underinvestigated by targeted capture panel-based clinical testing strategies in six families. This included structural variants, with notable benefit of the WGS approach in repetitive regions demonstrated by a family with a hybrid gene and hemizygous missense variant involving the opsin genes, OPN1LW and OPN1MW. There was also benefit in investigation of the repetitive GC-rich ORF15 region of RPGR. Further molecular investigations were facilitated by focused assays in these regions. Deep intronic variants were identified in IQCB1 and ABCA4, with functional RNA based studies of the IQCB1 variant revealing activation of a cryptic splice acceptor site. While targeted capture panel-based methods are successful in achieving an efficient molecular diagnosis in a proportion of cases, this study highlights the additional benefit and clinical value that may be derived from WGS, focused assays and functional genomics in the highly heterogeneous IRDs.

Genome sequencing in congenital cataracts improves diagnostic yield.

Congenital cataracts are one of the major causes of childhood-onset blindness around the world. Genetic diagnosis provides benefits through avoidance of unnecessary tests, surveillance of extraocular features, and genetic family information. In this study, we demonstrate the value of genome sequencing in improving diagnostic yield in congenital cataract patients and families. We applied genome sequencing to investigate 20 probands with congenital cataracts. We examined the added value of genome sequencing across a total cohort of 52 probands, including 14 unable to be diagnosed using previous microarray and exome or panel-based approaches. Although exome or genome sequencing would have detected the variants in 35/52 (67%) of the cases, specific advantages of genome sequencing led to additional diagnoses in 10% (5/52) of the overall cohort, and we achieved an overall diagnostic rate of 77% (40/52). Specific benefits of genome sequencing were due to detection of small copy number variants (2), indels in repetitive regions (2) or single-nucleotide variants (SNVs) in GC-rich regions (1), not detectable on the previous microarray, exome sequencing, or panel-based approaches. In other cases, SNVs were identified in cataract disease genes, including those newly identified since our previous study. This study highlights the additional yield of genome sequencing in congenital cataracts.

TUBB3 Arg262His causes a recognizable syndrome including CFEOM3, facial palsy, joint contractures, and early-onset peripheral neuropathy.

Microtubules are formed from heterodimers of alpha- and beta-tubulin, each of which has multiple isoforms encoded by separate genes. Pathogenic missense variants in multiple different tubulin isoforms cause brain malformations. Missense mutations in TUBB3, which encodes the neuron-specific beta-tubulin isotype, can cause congenital fibrosis of the extraocular muscles type 3 (CFEOM3) and/or malformations of cortical development, with distinct genotype-phenotype correlations. Here, we report fourteen individuals from thirteen unrelated families, each of whom harbors the identical NM_006086.4 (TUBB3):c.785G>A (p.Arg262His) variant resulting in a phenotype we refer to as the TUBB3 R262H syndrome. The affected individuals present at birth with ptosis, ophthalmoplegia, exotropia, facial weakness, facial dysmorphisms, and, in most cases, distal congenital joint contractures, and subsequently develop intellectual disabilities, gait disorders with proximal joint contractures, Kallmann syndrome (hypogonadotropic hypogonadism and anosmia), and a progressive peripheral neuropathy during the first decade of life. Subsets may also have vocal cord paralysis, auditory dysfunction, cyclic vomiting, and/or tachycardia at rest. All fourteen subjects share a recognizable set of brain malformations, including hypoplasia of the corpus callosum and anterior commissure, basal ganglia malformations, absent olfactory bulbs and sulci, and subtle cerebellar malformations. While similar, individuals with the TUBB3 R262H syndrome can be distinguished from individuals with the TUBB3 E410K syndrome by the presence of congenital and acquired joint contractures, an earlier onset peripheral neuropathy, impaired gait, and basal ganglia malformations.

Ensuring best practice in genomics education and evaluation: reporting item standards for education and its evaluation in genomics (RISE2 Genomics).

PURPOSE: Widespread, quality genomics education for health professionals is required to create a competent genomic workforce. A lack of standards for reporting genomics education and evaluation limits the evidence base for replication and comparison. We therefore undertook a consensus process to develop a recommended minimum set of information to support consistent reporting of design, development, delivery, and evaluation of genomics education interventions. METHODS: Draft standards were derived from literature (25 items from 21 publications). Thirty-six international experts were purposively recruited for three rounds of a modified Delphi process to reach consensus on relevance, clarity, comprehensiveness, utility, and design. RESULTS: The final standards include 18 items relating to development and delivery of genomics education interventions, 12 relating to evaluation, and 1 on stakeholder engagement. CONCLUSION: These Reporting Item Standards for Education and its Evaluation in Genomics (RISE2 Genomics) are intended to be widely applicable across settings and health professions. Their use by those involved in reporting genomics education interventions and evaluation, as well as adoption by journals and policy makers as the expected standard, will support greater transparency, consistency, and comprehensiveness of reporting. Consequently, the genomics education evidence base will be more robust, enabling high-quality education and evaluation across diverse settings.

PPA2-associated sudden cardiac death: extending the clinical and allelic spectrum in 20 new families.

PURPOSE: Biallelic hypomorphic variants in PPA2, encoding the mitochondrial inorganic pyrophosphatase 2 protein, have been recently identified in individuals presenting with sudden cardiac death, occasionally triggered by alcohol intake or a viral infection. Here we report 20 new families harboring PPA2 variants. METHODS: Synthesis of clinical and molecular data concerning 34 individuals harboring five previously reported PPA2 variants and 12 novel variants, 11 of which were functionally characterized. RESULTS: Among the 34 individuals, only 6 remain alive. Twenty-three died before the age of 2 years while five died between 14 and 16 years. Within these 28 cases, 15 died of sudden cardiac arrest and 13 of acute heart failure. One case was diagnosed prenatally with cardiomyopathy. Four teenagers drank alcohol before sudden cardiac arrest. Progressive neurological signs were observed in 2/6 surviving individuals. For 11 variants, recombinant PPA2 enzyme activities were significantly decreased and sensitive to temperature, compared to wild-type PPA2 enzyme activity. CONCLUSION: We expand the clinical and mutational spectrum associated with PPA2 dysfunction. Heart failure and sudden cardiac arrest occur at various ages with inter- and intrafamilial phenotypic variability, and presentation can include progressive neurological disease. Alcohol intake can trigger cardiac arrest and should be strictly avoided.

Paediatric genomic testing: Navigating medicare rebatable genomic testing.

Genomic testing for a genetic diagnosis is becoming standard of care for many children, especially those with a syndromal intellectual disability. While previously this type of specialised testing was performed mainly by clinical genetics teams, it is increasingly being 'mainstreamed' into standard paediatric care. With the introduction of a new Medicare rebate for genomic testing in May 2020, this type of testing is now available for paediatricians to order, in consultation with clinical genetics. Children must be aged less than 10 years with facial dysmorphism and multiple congenital abnormalities or have global developmental delay or moderate to severe intellectual disability. This rebate should increase the likelihood of a genetic diagnosis, with accompanying benefits for patient management, reproductive planning and diagnostic certainty. Similar to the introduction of chromosomal microarray into mainstream paediatrics, this genomic testing will increase the number of genetic diagnoses, however, will also yield more variants of uncertain significance, incidental findings, and negative results. This paper aims to guide paediatricians through the process of genomic testing, and represents the combined expertise of educators, clinical geneticists, paediatricians and genomic pathologists around Australia. Its purpose is to help paediatricians navigate choosing the right genomic test, consenting patients and understanding the possible outcomes of testing.

Targeted knockout of a chemokine-like gene increases anxiety and fear responses.

Emotional responses, such as fear and anxiety, are fundamentally important behavioral phenomena with strong fitness components in most animal species. Anxiety-related disorders continue to represent a major unmet medical need in our society, mostly because we still do not fully understand the mechanisms of these diseases. Animal models may speed up discovery of these mechanisms. The zebrafish is a highly promising model organism in this field. Here, we report the identification of a chemokine-like gene family, samdori (sam), and present functional characterization of one of its members, sam2 We show exclusive mRNA expression of sam2 in the CNS, predominantly in the dorsal habenula, telencephalon, and hypothalamus. We found knockout (KO) zebrafish to exhibit altered anxiety-related responses in the tank, scototaxis and shoaling assays, and increased crh mRNA expression in their hypothalamus compared with wild-type fish. To investigate generalizability of our findings to mammals, we developed a Sam2 KO mouse and compared it to wild-type littermates. Consistent with zebrafish findings, homozygous KO mice exhibited signs of elevated anxiety. We also found bath application of purified SAM2 protein to increase inhibitory postsynaptic transmission onto CRH neurons of the paraventricular nucleus. Finally, we identified a human homolog of SAM2, and were able to refine a candidate gene region encompassing SAM2, among 21 annotated genes, which is associated with intellectual disability and autism spectrum disorder in the 12q14.1 deletion syndrome. Taken together, these results suggest a crucial and evolutionarily conserved role of sam2 in regulating mechanisms associated with anxiety.

Revealing hidden genetic diagnoses in the ocular anterior segment disorders.

PURPOSE: Ocular anterior segment disorders (ASDs) are clinically and genetically heterogeneous, and genetic diagnosis often remains elusive. In this study, we demonstrate the value of a combined analysis protocol using phenotypic, genomic, and pedigree structure data to achieve a genetic conclusion. METHODS: We utilized a combination of chromosome microarray, exome sequencing, and genome sequencing with structural variant and trio analysis to investigate a cohort of 41 predominantly sporadic cases. RESULTS: We identified likely causative variants in 54% (22/41) of cases, including 51% (19/37) of sporadic cases and 75% (3/4) of cases initially referred as familial ASD. Two-thirds of sporadic cases were found to have heterozygous variants, which in most cases were de novo. Approximately one-third (7/22) of genetic diagnoses were found in rarely reported or recently identified ASD genes including PXDN, GJA8, COL4A1, ITPR1, CPAMD8, as well as the new phenotypic association of Axenfeld-Rieger anomaly with a homozygous ADAMTS17 variant. The remainder of the variants were in key ASD genes including FOXC1, PITX2, CYP1B1, FOXE3, and PAX6. CONCLUSIONS: We demonstrate the benefit of detailed phenotypic, genomic, variant, and segregation analysis to uncover some of the previously "hidden" heritable answers in several rarely reported and newly identified ocular ASD-related disease genes.

A set of regulatory genes co-expressed in embryonic human brain is implicated in disrupted speech development.

Genetic investigations of people with impaired development of spoken language provide windows into key aspects of human biology. Over 15 years after FOXP2 was identified, most speech and language impairments remain unexplained at the molecular level. We sequenced whole genomes of nineteen unrelated individuals diagnosed with childhood apraxia of speech, a rare disorder enriched for causative mutations of large effect. Where DNA was available from unaffected parents, we discovered de novo mutations, implicating genes, including CHD3, SETD1A and WDR5. In other probands, we identified novel loss-of-function variants affecting KAT6A, SETBP1, ZFHX4, TNRC6B and MKL2, regulatory genes with links to neurodevelopment. Several of the new candidates interact with each other or with known speech-related genes. Moreover, they show significant clustering within a single co-expression module of genes highly expressed during early human brain development. This study highlights gene regulatory pathways in the developing brain that may contribute to acquisition of proficient speech.

Feasibility of Ultra-Rapid Exome Sequencing in Critically Ill Infants and Children With Suspected Monogenic Conditions in the Australian Public Health Care System.

Importance: Widespread adoption of rapid genomic testing in pediatric critical care requires robust clinical and laboratory pathways that provide equitable and consistent service across health care systems. Objective: To prospectively evaluate the performance of a multicenter network for ultra-rapid genomic diagnosis in a public health care system. Design, Setting, and Participants: Descriptive feasibility study of critically ill pediatric patients with suspected monogenic conditions treated at 12 Australian hospitals between March 2018 and February 2019, with data collected to May 2019. A formal implementation strategy emphasizing communication and feedback, standardized processes, coordination, distributed leadership, and collective learning was used to facilitate adoption. Exposures: Ultra-rapid exome sequencing. Main Outcomes and Measures: The primary outcome was time from sample receipt to ultra-rapid exome sequencing report. The secondary outcomes were the molecular diagnostic yield, the change in clinical management after the ultra-rapid exome sequencing report, the time from hospital admission to the laboratory report, and the proportion of laboratory reports returned prior to death or hospital discharge. Results: The study population included 108 patients with a median age of 28 days (range, 0 days to 17 years); 34% were female; and 57% were from neonatal intensive care units, 33% were from pediatric intensive care units, and 9% were from other hospital wards. The mean time from sample receipt to ultra-rapid exome sequencing report was 3.3 days (95% CI, 3.2-3.5 days) and the median time was 3 days (range, 2-7 days). The mean time from hospital admission to ultra-rapid exome sequencing report was 17.5 days (95% CI, 14.6-21.1 days) and 93 reports (86%) were issued prior to death or hospital discharge. A molecular diagnosis was established in 55 patients (51%). Eleven diagnoses (20%) resulted from using the following approaches to augment standard exome sequencing analysis: mitochondrial genome sequencing analysis, exome sequencing-based copy number analysis, use of international databases to identify novel gene-disease associations, and additional phenotyping and RNA analysis. In 42 of 55 patients (76%) with a molecular diagnosis and 6 of 53 patients (11%) without a molecular diagnosis, the ultra-rapid exome sequencing result was considered as having influenced clinical management. Targeted treatments were initiated in 12 patients (11%), treatment was redirected toward palliative care in 14 patients (13%), and surveillance for specific complications was initiated in 19 patients (18%). Conclusions and Relevance: This study suggests feasibility of ultra-rapid genomic testing in critically ill pediatric patients with suspected monogenic conditions in the Australian public health care system. However, further research is needed to understand the clinical value of such testing, and the generalizability of the findings to other health care settings.

Glibenclamide treatment in a Cantú syndrome patient with a pathogenic ABCC9 gain-of-function variant: Initial experience.

Cantú syndrome (CS), characterized by hypertrichosis, distinctive facial features, and complex cardiovascular abnormalities, is caused by pathogenic variants in ABCC9 and KCNJ8 genes. These genes encode gain-of-function mutations in the regulatory (SUR2) and pore-forming (Kir6.1) subunits of KATP channels, respectively, suggesting that channel-blocking sulfonylureas could be a viable therapy. Here we report a neonate with CS, carrying a heterozygous ABCC9 variant (c.3347G>A, p.Arg1116His), born prematurely at 32 weeks gestation. Initial echocardiogram revealed a large patent ductus arteriosus (PDA), and high pulmonary pressures with enlarged right ventricle. He initially received surfactant and continuous positive airway pressure ventilation and was invasively ventilated for 4 weeks, until PDA ligation. After surgery, he still had ongoing bilevel positive airway pressure (BiPAP) requirement, but was subsequently weaned to nocturnal BiPAP. He was treated for pulmonary hypertension with Sildenafil, but failed to make further clinical improvement. A therapeutic glibenclamide trial was commenced in week 11 (initial dose of 0.05 mg-1 kg-1 day-1 in two divided doses). After 1 week of treatment, he began to tolerate time off BiPAP when awake, and edema improved. Glibenclamide was well tolerated, and the dose was slowly increased to 0.15 mg-1 kg-1 day-1 over the next 12 weeks. Mild transient hypoglycemia was observed, but there was no cardiovascular dysfunction. Confirmation of therapeutic benefit will require studies of more CS patients but, based on this limited experience, consideration should be given to glibenclamide as CS therapy, although problems associated with prematurity, and complications of hypoglycemia, might limit outcome in critically ill neonates with CS.

Mutations in SIPA1L3 cause eye defects through disruption of cell polarity and cytoskeleton organization.

Correct morphogenesis and differentiation are critical in development and maintenance of the lens, which is a classic model system for epithelial development and disease. Through germline genomic analyses in patients with lens and eye abnormalities, we discovered functional mutations in the Signal Induced Proliferation Associated 1 Like 3 (SIPA1L3) gene, which encodes a previously uncharacterized member of the Signal Induced Proliferation Associated 1 (SIPA1 or SPA1) family, with a role in Rap1 signalling. Patient 1, with a de novo balanced translocation, 46,XY,t(2;19)(q37.3;q13.1), had lens and ocular anterior segment abnormalities. Breakpoint mapping revealed transection of SIPA1L3 at 19q13.1 and reduced SIPA1L3 expression in patient lymphoblasts. SIPA1L3 downregulation in 3D cell culture revealed morphogenetic and cell polarity abnormalities. Decreased expression of Sipa1l3 in zebrafish and mouse caused severe lens and eye abnormalities. Sipa1l3(-/-) mice showed disrupted epithelial cell organization and polarity and, notably, abnormal epithelial to mesenchymal transition in the lens. Patient 2 with cataracts was heterozygous for a missense variant in SIPA1L3, c.442G>T, p.Asp148Tyr. Examination of the p.Asp148Tyr mutation in an epithelial cell line showed abnormal clustering of actin stress fibres and decreased formation of adherens junctions. Our findings show that abnormalities of SIPA1L3 in human, zebrafish and mouse contribute to lens and eye defects, and we identify a critical role for SIPA1L3 in epithelial cell morphogenesis, polarity, adhesion and cytoskeletal organization.