Brain size regulations by cbp haploinsufficiency evaluated by in-vivo MRI based volumetry

The Rubinstein-Taybi Syndrome (RSTS) is a congenital disease that affects brain development causing severe cognitive deficits. In most cases the disease is associated with dominant mutations in the gene encoding the CREB binding protein (CBP). In this work, we present the first quantitative analysis of brain abnormalities in a mouse model of RSTS using magnetic resonance imaging (MRI) and two novel self-developed automated algorithms for image volumetric analysis. Our results quantitatively confirm key syndromic features observed in RSTS patients, such as reductions in brain size (-16.31%, p < 0.05), white matter volume (-16.00%, p < 0.05), and corpus callosum (-12.40%, p < 0.05). Furthermore, they provide new insight into the developmental origin of the disease. By comparing brain tissues in a region by region basis between cbp(+/-) and cbp(+/+) littermates, we found that cbp haploinsufficiency is specifically associated with significant reductions in prosencephalic tissue, such us in the olfactory bulb and neocortex, whereas regions evolved from the embryonic rhombencephalon were spared. Despite the large volume reductions, the proportion between gray-, white-matter and cerebrospinal fluid were conserved, suggesting a role of CBP in brain size regulation. The commonalities with holoprosencephaly and arhinencephaly conditions suggest the inclusion of RSTS in the family of neuronal migration disorders.We are grateful to Begona Fernandez for her excellent technical assistance. We would like to thank S. Sawiak (Wolfson Imaging Centre, University of Cambridge, Cambridge, United Kingdom) for the mouse brain tissue probability maps and the SPMmouse plug-in, and to N. Kovacevic (Mouse Imaging Centre, Hospital for Sick Children, Toronto, Ontario, Canada) for the atlas of the mouse brain. Supported by grants from the Spanish MINECO to S.C. (BFU 2012-39958) and MINECO and FEDER to D.M. (TEC 2012-33778) and from MINECO (SAF2011-22855) and Generalitat Valenciana (Prometeo/2012/005) to A.B. The Instituto de Neurociencias is "Centre of Excellence Severo Ochoa".Ateca Cabarga, JC.; Cosa, A.; Pallares, V.; Lopez-Atalaya, JP.; Barco, A.; Canals, S.; Moratal Pérez, D. (2015). Brain size regulations by cbp haploinsufficiency evaluated by in-vivo MRI based volumetry. Scientific Reports. 5. https://doi.org/10.1038/srep16256S5Rubinstein, J. H. & Taybi, H. Broad thumbs and toes and facial abnormalities. A possible mental retardation syndrome. Am J Dis Child 105, 588–608 (1963).Van Belzen, M., Bartsch, O., Lacombe, D., Peters, D. J. & Hennekam, R. C. Rubinstein-Taybi syndrome (CREBBP, EP300). Eur J Hum Genet. 19, preceeding 118–120 (2011).Hennekam, R. C. 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A Solve-RD ClinVar-based reanalysis of 1522 index cases from ERN-ITHACA reveals common pitfalls and misinterpretations in exome sequencing

Purpose Within the Solve-RD project (https://solve-rd.eu/), the European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies aimed to investigate whether a reanalysis of exomes from unsolved cases based on ClinVar annotations could establish additional diagnoses. We present the results of the “ClinVar low-hanging fruit” reanalysis, reasons for the failure of previous analyses, and lessons learned. Methods Data from the first 3576 exomes (1522 probands and 2054 relatives) collected from European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies was reanalyzed by the Solve-RD consortium by evaluating for the presence of single-nucleotide variant, and small insertions and deletions already reported as (likely) pathogenic in ClinVar. Variants were filtered according to frequency, genotype, and mode of inheritance and reinterpreted. Results We identified causal variants in 59 cases (3.9%), 50 of them also raised by other approaches and 9 leading to new diagnoses, highlighting interpretation challenges: variants in genes not known to be involved in human disease at the time of the first analysis, misleading genotypes, or variants undetected by local pipelines (variants in off-target regions, low quality filters, low allelic balance, or high frequency). Conclusion The “ClinVar low-hanging fruit” analysis represents an effective, fast, and easy approach to recover causal variants from exome sequencing data, herewith contributing to the reduction of the diagnostic deadlock

PHYSICAL ADAPTATION OF CHILDREN TO LIFE AT HIGH-ALTITUDE

Children permanently exposed to hypoxia at altitudes of > 3000 m above sea level show a phenotypical form of adaptation. Under these environmental conditions, oxygen uptake in the lungs is enhanced by increases in ventilation, lung compliance, and pulmonary diffusion. Lung and thorax volumes in children growing up at high altitude are increased. The haemoglobin concentration in highlanders is elevated. With respect to the decreased arterial oxygen tension at high altitude, this seems a useful adaptation. Blood viscosity also increases as a result of the increase in red blood cell concentrations however, and this has potentially negative effects on the microcirculation in the tissues. The decreased partial pressure of oxygen in the lungs of highland children is associated with a higher pulmonary artery pressure. Pulmonary hypertension, high altitude pulmonary oedema, and chronic mountain sickness form part of the pathophysiology afflicting highland dwellers. Birth weight at high altitude is decreased. Decreased postnatal growth has been widely reported in populations at high altitude, particularly in early studies from the Andes. Recent studies taking into account the effects of socio-economic deprivation, suggest that long-term exposure to altitudes of 2500-3900 m is associated with a moderate reduction in linear growth in children