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Cerebral palsy (CP), a neurodevelopmental disorder characterized by irreversible, nonprogressive central motor dysfunction, is commonly associated with prematurity or perinatal brain injury. However, accumulating evidence suggests deleterious genomic variants may contribute to CP in addition to environmental insults. To identify genes contributing to risk for CP, we performed whole-exome sequencing on 250 parent-offspring CP trios. We identified a significant contribution of damaging de novo mutations (DNMs), especially in genes that are intolerant to loss of function mutations. Eight genes had multiple, independently-arising damaging DNMs, including two novel CP-associated genes, FBXO31 and RHOB, and four genes previously implicated in cerebral palsy phenotypes, TUBA1A, CTNNB1, SPAST, and ATL1. Functional experiments, including molecular and biochemical assays and patient fibroblast studies indicate that the recurrent RHOB mutation identified in patients enhances Rho effector binding in the active state and that the FBXO31 mutation leads to elevated levels of cyclin D. Analysis of candidate CP risk genes highlighted genetic overlap with hereditary spastic paraplegia as well as intellectual disability, autism, and epilepsy, converging with epidemiologic findings. Computational network analysis of risk genes identified significant enrichment of Rho GTPase, extracellular matrix, focal adhesions, cytoskeleton, and cell projection pathways. CP risk genes in Rho GTPase, cytoskeleton and cell projection pathways were found to play an important role in neuromotor development via a Drosophila reverse genetics screen. Based on enrichment analysis, we estimate that an excess of damaging de novo and inherited recessive variants collectively account for ~14% of the cases in our cohort, whereas perinatal asphyxia is currently estimated to occur in 8-10% of CP cases. Together, these findings provide evidence for the role of genetically-mediated dysregulation of early brain connectivity in CP.

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BackgroundTwin-to-twin transfusion syndrome (TTTS) is a serious complication of 10–15% of twin or triplet pregnancies in which multiple fetuses share a single placenta. Communicating placental vessels allow one fetus (the donor) to pump blood to the other (the recipient). Mortality rates without intervention are high, approaching 100% in some series, with fetal deaths usually due to cardiac failure. Surgical correction using laser photocoagulation of communicating placental vessels was developed in the 1980s and refined in the 1990s. Since it was introduced in Victoria in 2006, laser surgery has been performed in approximately 120 pregnancies.Survival of one or more fetuses following laser surgery is currently > 90%, however the neurodevelopmental outcomes for survivors remain incompletely understood. Prior to laser therapy, at least one in five survivors of TTTS had serious adverse neurodevelopmental outcomes (usually cerebral palsy). Current estimates of neurological impairment among survivors following laser surgery vary from 4 to 31% and long-term follow-up data are limited.MethodsThis paper describes the methodology for a retrospective cohort study in which children aged 24 months and over (corrected for prematurity), who were treated with laser placental photocoagulation for TTTS at Monash Health in Victoria, Australia, will undergo comprehensive neurodevelopmental assessment by a multidisciplinary team. Evaluation will include parental completion of pre-assessment questionnaires of social and behavioural development, a standardised medical assessment by a developmental paediatrician or paediatric neurologist, and age-appropriate cognitive and academic, speech and fine and gross motor assessments by psychologists, speech and occupational therapists or physiotherapists. Assessments will be undertaken at the Murdoch Children’s Research Institute/Royal Children’s Hospital, at Monash Health or at another mutually agreed location. Results will be recorded in a secure online database which will facilitate future related research.DiscussionThis will be the first study to report and evaluate neurodevelopmental outcomes following laser surgery for twin-to-twin transfusion syndrome in Victoria, and will inform clinical practice regarding follow-up of children at risk of adverse outcomes.Electronic supplementary materialThe online version of this article (10.1186/s12887-018-1230-8) contains supplementary material, which is available to authorized users.