Math1 Is Essential for the Development of Hindbrain Neurons Critical for Perinatal Breathing

SummaryMice lacking the proneural transcription factor Math1 (Atoh1) lack multiple neurons of the proprioceptive and arousal systems and die shortly after birth from an apparent inability to initiate respiration. We sought to determine whether Math1 was necessary for the development of hindbrain nuclei involved in respiratory rhythm generation, such as the parafacial respiratory group/retrotrapezoid nucleus (pFRG/RTN), defects in which are associated with congenital central hypoventilation syndrome (CCHS). We generated a Math1-GFP fusion allele to trace the development of Math1-expressing pFRG/RTN and paratrigeminal neurons and found that loss of Math1 did indeed disrupt their migration and differentiation. We also identified Math1-dependent neurons and their projections near the pre-Bötzinger complex, a structure critical for respiratory rhythmogenesis, and found that glutamatergic modulation reestablished a rhythm in the absence of Math1. This study identifies Math1-dependent neurons that are critical for perinatal breathing that may link proprioception and arousal with respiration

Exploring the Mechanism Responsible for Cellulase Thermostability by Structure-Guided Recombination

Cellulases from Bacillus and Geobacillus bacteria are potentially useful in the biofuel and animal feed industries. One of the unique characteristics of these enzymes is that they are usually quite thermostable. We previously identified a cellulase, GsCelA, from thermophilic Geobacillus sp. 70PC53, which is much more thermostable than its Bacillus homolog, BsCel5A. Thus, these two cellulases provide a pair of structures ideal for investigating the mechanism regarding how these cellulases can retain activity at high temperature. In the present study, we applied the SCHEMA non-contiguous recombination algorithm as a novel tool, which assigns protein sequences into blocks for domain swapping in a way that lessens structural disruption, to generate a set of chimeric proteins derived from the recombination of GsCelA and BsCel5A. Analyzing the activity and thermostability of this designed library set, which requires only a limited number of chimeras by SCHEMA calculations, revealed that one of the blocks may contribute to the higher thermostability of GsCelA. When tested against swollen Avicel, the highly thermostable chimeric cellulase C10 containing this block showed significantly higher activity (22%-43%) and higher thermostability compared to the parental enzymes. With further structural determinations and mutagenesis analyses, a 3_(10) helix was identified as being responsible for the improved thermostability of this block. Furthermore, in the presence of ionic calcium and crown ether (CR), the chimeric C10 was found to retain 40% residual activity even after heat treatment at 90°C. Combining crystal structure determinations and structure-guided SCHEMA recombination, we have determined the mechanism responsible for the high thermostability of GsCelA, and generated a novel recombinant enzyme with significantly higher activity

Exome Sequencing Implicates Ancestry-Related Mendelian Variation at SYNE1 in Childhood-Onset Essential Hypertension

Childhood-onset essential hypertension (COEH) is an uncommon form of hypertension that manifests in childhood or adolescence and, in the United States, disproportionately affects children of African ancestry. The etiology of COEH is unknown, but its childhood onset, low prevalence, high heritability, and skewed ancestral demography suggest the potential to identify rare genetic variation segregating in a Mendelian manner among affected individuals and thereby implicate genes important to disease pathogenesis. However, no COEH genes have been reported to date. Here, we identify recessive segregation of rare and putatively damaging missense variation in the spectrin domain of spectrin repeat containing nuclear envelope protein 1 (SYNE1), a cardiovascular candidate gene, in 3 of 16 families with early-onset COEH without an antecedent family history. By leveraging exome sequence data from an additional 48 COEH families, 1,700 in-house trios, and publicly available data sets, we demonstrate that compound heterozygous SYNE1 variation in these COEH individuals occurred more often than expected by chance and that this class of biallelic rare variation was significantly enriched among individuals of African genetic ancestry. Using in vitro shRNA knockdown of SYNE1, we show that reduced SYNE1 expression resulted in a substantial decrease in the elasticity of smooth muscle vascular cells that could be rescued by pharmacological inhibition of the downstream RhoA/Rho-associated protein kinase pathway. These results provide insights into the molecular genetics and underlying pathophysiology of COEH and suggest a role for precision therapeutics in the future

Comparisons between Full-time and Part-time Pediatric Emergency Physicians in Pediatric Emergency Department

Pediatric emergency medicine is a young field that has established itself in recent decades. Many unanswered questions remain regarding how to deliver better pediatric emergency care. The implementation of full-time pediatric emergency physicians is a quality improvement strategy for child care in Taiwan. The aim of this study is to evaluate the quality of care under different physician coverage models in the pediatric emergency department (ED). Methods: The medical records of 132,398 patients visiting the pediatric ED of a tertiary care university hospital during January 2004 to December 2006 were retrospectively reviewed. Full-time pediatric emergency physicians are the group specializing in the pediatric emergency medicine, and they only work in the pediatric ED. Part-time pediatricians specializing in other subspecialties also can work an extra shift in the pediatric ED, with the majority working in their inpatient and outpatient services. We compared quality performance indicators, including: mortality rate, the 72-hour return visit rate, length of stay, admission rate, and the rate of being kept for observation between full-time and part-time pediatric emergency physicians. Results: An average of 3678 ± 125 [mean ± standard error (SE)] visits per month (with a range of 2487–6646) were observed. The trends in quality of care, observed monthly, indicated that the 72-hour return rate was 2–6% and length of stay in the ED decreased from 11.5 hours to 3.2 hours over the study period. The annual mortality rate within 48 hours of admission to the ED increased from 0.04% to 0.05% and then decreased to 0.02%, and the overall mortality rate dropped from 0.13% to 0.07%. Multivariate analyses indicated that there was no change in the 72-hour return visit rate for full-time pediatric emergency physicians; they were more likely to admit and keep patients for observation [odds ratio = 1.43 and odds ratio = 1.71, respectively], and these results were similar to those of senior physicians. Conclusion: Full-time pediatric emergency physicians in the pediatric ED decreased the mortality rate and length of stay in the ED, but had no change in the 72-hour return visit rate. This pilot study shows that the quality of care in pediatric ED after the implementation of full-time pediatric emergency physicians needs further evaluation

A partial loss of function allele of Methyl-CpG-binding protein 2 predicts a human neurodevelopmental syndrome

Rett Syndrome, an X-linked dominant neurodevelopmental disorder characterized by regression of language and hand use, is primarily caused by mutations in methyl-CpG-binding protein 2 (MECP2). Loss of function mutations in MECP2 are also found in other neurodevelopmental disorders such as autism, Angelman-like syndrome and non-specific mental retardation. Furthermore, duplication of the MECP2 genomic region results in mental retardation with speech and social problems. The common features of human neurodevelopmental disorders caused by the loss or increase of MeCP2 function suggest that even modest alterations of MeCP2 protein levels result in neurodevelopmental problems. To determine whether a small reduction in MeCP2 level has phenotypic consequences, we characterized a conditional mouse allele of Mecp2 that expresses 50% of the wild-type level of MeCP2. Upon careful behavioral analysis, mice that harbor this allele display a spectrum of abnormalities such as learning and motor deficits, decreased anxiety, altered social behavior and nest building, decreased pain recognition and disrupted breathing patterns. These results indicate that precise control of MeCP2 is critical for normal behavior and predict that human neurodevelopmental disorders will result from a subtle reduction in MeCP2 expression

Model Organisms Facilitate Rare Disease Diagnosis and Therapeutic Research.

Efforts to identify the genetic underpinnings of rare undiagnosed diseases increasingly involve the use of next-generation sequencing and comparative genomic hybridization methods. These efforts are limited by a lack of knowledge regarding gene function, and an inability to predict the impact of genetic variation on the encoded protein function. Diagnostic challenges posed by undiagnosed diseases have solutions in model organism research, which provides a wealth of detailed biological information. Model organism geneticists are by necessity experts in particular genes, gene families, specific organs, and biological functions. Here, we review the current state of research into undiagnosed diseases, highlighting large efforts in North America and internationally, including the Undiagnosed Diseases Network (UDN) (Supplemental Material, File S1) and UDN International (UDNI), the Centers for Mendelian Genomics (CMG), and the Canadian Rare Diseases Models and Mechanisms Network (RDMM). We discuss how merging human genetics with model organism research guides experimental studies to solve these medical mysteries, gain new insights into disease pathogenesis, and uncover new therapeutic strategies