Chromosome silencing in vitro reveals trisomy 21 causes cell-autonomous deficits in angiogenesis and early dysregulation in Notch signaling.

Despite the prevalence of Down syndrome (DS), little is known regarding the specific cell pathologies that underlie this multi-system disorder. To understand which cell types and pathways are more directly affected by trisomy 21 (T21), we used an inducible-XIST system to silence one chromosome 21 in vitro. T21 caused the dysregulation of Notch signaling in iPSCs, potentially affecting cell-type programming. Further analyses identified dysregulation of pathways important for two cell types: neurogenesis and angiogenesis. Angiogenesis is essential to many bodily systems, yet is understudied in DS; therefore, we focused next on whether T21 affects endothelial cells. An in vitro assay for microvasculature formation revealed a cellular pathology involving delayed tube formation in response to angiogenic signals. Parallel transcriptomic analysis of endothelia further showed deficits in angiogenesis regulators. Results indicate a direct cell-autonomous impact of T21 on endothelial function, highlighting the importance of angiogenesis, with wide-reaching implications for development and disease progression.

Developing a Culture of Mentorship to Strengthen Academic Medical Centers.

Mentorship is central to academic medicine and its missions, and it has long played a critical role in the training and career development of physicians and scientists. A growing body of literature has documented the positive impact of mentorship on various outcomes, including research productivity, academic promotion, faculty retention, and career satisfaction. These benefits span academic medical centers' missions and have the potential to enhance biomedical research, patient care, education, and faculty diversity and leadership.In this Invited Commentary, the authors argue that a dynamic culture of mentorship is essential to the success of academic medical centers and should be elevated to the level of a major strategic priority. This culture of mentorship would capitalize on an institution's intellectual resources and seek to develop leaders in biomedical discovery, patient care, and education. The bidirectional transmission of knowledge between mentors and mentees, through both formal programs and informal relationships, can foster the growth of faculty members needed to meet the complex challenges currently confronting medical schools and teaching hospitals.Developing a culture of mentorship requires a strong commitment by leaders at all levels to nurture the next generation of physicians and scientists as well as grassroots efforts by trainees and faculty to seek out and create mentorship opportunities. The authors conclude by outlining possible mechanisms and incentives for elevating mentorship to the level of a strategic priority to strengthen academic medical centers across their missions.

Novel germline mutation (Leu512Met) in the thyrotropin receptor gene (TSHR) leading to sporadic non-autoimmune hyperthyroidism.

BACKGROUND: Primary nonautoimmune hyperthyroidism is a rare cause of neonatal hyperthyroidism. This results from an activating mutation in the thyrotropin-receptor (TSHR). It can be inherited in an autosomal dominant manner or occur sporadically as a de novo mutation. Affected individuals display a wide phenotype from severe neonatal to mild subclinical hyperthyroidism. We describe a 6-month-old boy with a de novo mutation in the TSHR gene who presented with accelerated growth, enlarging head circumference, tremor and thyrotoxicosis. METHODS: Genomic DNA from the patient's and parents' peripheral blood leukocytes was extracted. Exons 9 and 10 of the TSHR gene were amplified by PCR and sequenced. RESULTS: Sequencing exon 10 of the TSHR gene revealed a novel heterozygous missense mutation substituting cytosine to adenine at nucleotide position 1534 in the patient's peripheral blood leukocytes. This leads to a substitution of leucine to methionine at amino acid position 512. The mutation was absent in the parents. In silico modeling by PolyPhen-2 and SIFT predicted the mutation to be deleterious. CONCLUSIONS: The p.Leu512Met mutation (c.1534C>A) of the TSHR gene has not been previously described in germline or somatic mutations. This case presentation highlights the possibility of mild thyrotoxicosis in affected individuals and contributes to the understanding of sporadic non-autoimmune primary hyperthyroidism.

Structural forms of the human amylase locus and their relationships to SNPs, haplotypes and obesity.

Hundreds of genes reside in structurally complex, poorly understood regions of the human genome. One such region contains the three amylase genes (AMY2B, AMY2A and AMY1) responsible for digesting starch into sugar. Copy number of AMY1 is reported to be the largest genomic influence on obesity, although genome-wide association studies for obesity have found this locus unremarkable. Using whole-genome sequence analysis, droplet digital PCR and genome mapping, we identified eight common structural haplotypes of the amylase locus that suggest its mutational history. We found that the AMY1 copy number in an individual's genome is generally even (rather than odd) and partially correlates with nearby SNPs, which do not associate with body mass index (BMI). We measured amylase gene copy number in 1,000 obese or lean Estonians and in 2 other cohorts totaling ∼3,500 individuals. We had 99% power to detect the lower bound of the reported effects on BMI, yet found no association.

Heterozygous mutations in natriuretic peptide receptor-B (NPR2) gene as a cause of short stature.

Based on the observation of reduced stature in relatives of patients with acromesomelic dysplasia, Maroteaux type (AMDM), caused by homozygous or compound heterozygous mutations in natriuretic peptide receptor-B gene (NPR2), it has been suggested that heterozygous mutations in this gene could be responsible for the growth impairment observed in some cases of idiopathic short stature (ISS). We enrolled 192 unrelated patients with short stature and 192 controls of normal height and identified seven heterozygous NPR2 missense or splice site mutations all in the short stature patients, including one de novo splice site variant. Three of the six inherited variants segregated with short stature in the family. Nine additional rare nonsynonymous NPR2 variants were found in three additional cohorts. Functional studies identified eight loss-of-function mutations in short individuals and one gain-of-function mutation in tall individuals. With these data, we were able to rigorously verify that NPR2 functional haploinsufficiency contributes to short stature. We estimate a prevalence of NPR2 haploinsufficiency of between 0 and 1/26 in people with ISS. We suggest that NPR2 gain of function may be a more common cause of tall stature than previously recognized.

Functional significance of single nucleotide polymorphisms in the lactase gene in diverse US patients and evidence for a novel lactase persistence allele at -13909 in those of European ancestry.

OBJECTIVES: Recent data from mainly homogeneous European and African populations implicate a 140-bp region 5' to the transcriptional start site of LCT (the lactase gene) as a regulatory site for lactase persistence and nonpersistence. Because there are no studies of US nonhomogeneous populations, we performed genotype/phenotype analysis of the -13910 and -22018 LCT single nucleotide polymorphisms (SNPs) in New England children, mostly of European ancestry. METHODS: Duodenal biopsies were processed for disaccharidase activities, RNA quantification by reverse transcription polymerase chain reaction (RT-PCR), allelic expression ratios by PCR, and genotyping and SNP analysis. Results were compared with clinical information. RESULTS: Lactase activity and mRNA levels, and sucrase-to-lactase ratios of enzyme activity and mRNA, showed robust correlations with genotype. None of the other LCT SNPs showed as strong a correlation with enzyme or mRNA levels as did -13910. Data were consistent, with the -13910 being the causal sequence variant instead of -22018. Four individuals heterozygous for -13910T/C had allelic expression patterns similar to individuals with -13910C/C genotypes; of these, 2 showed equal LCT expression from the 2 alleles and a novel variant (-13909C>A) associated with lactase persistence. CONCLUSIONS: The identification of -13910C/C genotype is likely to predict lactase nonpersistence, consistent with prior published studies. A -13910T/T genotype will frequently, but not perfectly, predict lactase persistence in this mixed European-ancestry population; a -13910T/C genotype will not predict the phenotype. A long, rare haplotype in 2 individuals with -13910T/C genotype but equal allele-specific expression contains a novel lactase persistence allele present at -13909.

Diversity efforts, admissions, and national rankings: can we align priorities?

BACKGROUND: Increasing student body diversity is a priority for national health education and professional organizations and for many medical schools. However, national rankings of medical schools, such as those published by U.S. News & World Report, place a heavy emphasis on grade point average (GPA) and Medical College Admissions Test (MCAT) scores, without considering student body diversity. These rankings affect organizational reputation and admissions outcomes, even though there is considerable controversy surrounding the predictive value of GPA and MCAT scores. SUMMARY: Our aim in this article was to explore the relationship between standard admissions practices, which typically aim to attract students with the highest academic scores, and student body diversity. We examined how changes in GPA and MCAT scores over 5 years correlated with the percentage of enrolled students who are underrepresented in medicine. In a majority of medical schools in the United States from 2005 to 2009, average GPA and MCAT scores of applicants increased, whereas the percentage of enrolled students who are underrepresented in medicine decreased. CONCLUSIONS: Our findings suggest that efforts to increase the diversity of medical school student bodies may be complicated by a desire to maintain high average GPA and MCAT scores. We propose that U.S. News revise its ranking methodology by incorporating a new diversity score into its student selectivity score and by reducing the weight placed on GPA and MCAT scores.

Whole exome sequencing to identify genetic causes of short stature.

BACKGROUND/AIMS: Short stature is a common reason for presentation to pediatric endocrinology clinics. However, for most patients, no cause for the short stature can be identified. As genetics plays a strong role in height, we sought to identify known and novel genetic causes of short stature. METHODS: We recruited 14 children with severe short stature of unknown etiology. We conducted whole exome sequencing of the patients and their family members. We used an analysis pipeline to identify rare non-synonymous genetic variants that cause the short stature. RESULTS: We identified a genetic cause of short stature in 5 of the 14 patients. This included cases of floating-harbor syndrome, Kenny-Caffey syndrome, the progeroid form of Ehlers-Danlos syndrome, as well as 2 cases of the 3-M syndrome. For the remaining patients, we have generated lists of candidate variants. CONCLUSIONS: Whole exome sequencing can help identify genetic causes of short stature in the context of defined genetic syndromes, but may be less effective in identifying novel genetic causes of short stature in individual families. Utilized in the clinic, whole exome sequencing can provide clinically relevant diagnoses for these patients. Rare syndromic causes of short stature may be underrecognized and underdiagnosed in pediatric endocrinology clinics.

Lipids, safety parameters, and drug concentrations after an additional 2 years of treatment with anacetrapib in the DEFINE study.

Anacetrapib is a cholesteryl ester transfer protein (CETP) inhibitor that has previously been shown to reduce low-density lipoprotein cholesterol (LDL-C) and raise high-density lipoprotein cholesterol (HDL-C) in patients with or at high risk of coronary heart disease in the 76-week, placebo-controlled, Determining the Efficacy and Tolerability of CETP Inhibition with Anacetrapib (DEFINE) trial. Here, we report the results of the 2-year extension to the DEFINE study where patients (n = 803) continued on the same assigned treatment as in the original 76-week study. Treatment with anacetrapib during the 2-year extension was well tolerated with a safety profile similar to patients on placebo. No clinically important abnormalities in liver enzymes, blood pressure, electrolytes, or adverse experiences were observed during the extension. At the end of the extension study, relative to the original baseline value, anacetrapib reduced Friedewald-calculated LDL-C by 39.9% and increased HDL-C by 153.3%, compared to placebo. The apparent steady state mean plasma trough concentration of anacetrapib was ∼640 nmol/L. Geometric mean plasma concentrations of anacetrapib did not appear to increase beyond week 40 of the 2-year extension of the 76-week DEFINE base study. In conclusion, an additional 2 years of treatment with anacetrapib were well tolerated with durable lipid-modifying effects on LDL-C and HDL-C.

Evaluation of lipids, drug concentration, and safety parameters following cessation of treatment with the cholesteryl ester transfer protein inhibitor anacetrapib in patients with or at high risk for coronary heart disease.

The aim of this study was to assess the effects on lipids and safety during a 12-week reversal period after 18 months of treatment with anacetrapib. The cholesteryl ester transfer protein inhibitor anacetrapib was previously shown to reduce low-density lipoprotein cholesterol by 39.8% (estimated using the Friedewald equation) and increase high-density lipoprotein (HDL) cholesterol by 138.1%, with an acceptable side-effect profile, in patients with or at high risk for coronary heart disease in the Determining the Efficacy and Tolerability of CETP Inhibition With Anacetrapib (DEFINE) trial. A total of 1,398 patients entered the 12-week reversal-phase study, either after completion of the active-treatment phase or after early discontinuation of the study medication. In patients allocated to anacetrapib, placebo-adjusted mean percentage decreases from baseline were observed at 12 weeks off the study drug for Friedewald-calculated low-density lipoprotein cholesterol (18.6%), non-HDL cholesterol (17.6%), and apolipoprotein B (10.2%); placebo-adjusted mean percentage increases were observed for HDL cholesterol (73.0%) and apolipoprotein A-I (24.5%). Residual plasma anacetrapib levels (about 40% of on-treatment apparent steady-state trough levels) were also detected 12 weeks after cessation of anacetrapib. No clinically important elevations in liver enzymes, blood pressure, electrolytes, or adverse experiences were observed during the reversal phase. Preliminary data from a small cohort (n = 30) revealed the presence of low concentrations of anacetrapib in plasma 2.5 to 4 years after the last anacetrapib dose. In conclusion, after the cessation of active treatment, anacetrapib plasma lipid changes and drug levels decreased to approximately 40% of on-treatment trough levels at 12 weeks after dosing, but modest HDL cholesterol elevations and low drug concentrations were still detectable 2 to 4 years after the last dosing.

A novel deletion of IGF1 in a patient with idiopathic short stature provides insight Into IGF1 haploinsufficiency.

CONTEXT: Short stature is a common reason for referral to pediatric endocrinology centers. Frequently, the underlying etiology of short stature is unknown, resulting in a diagnosis of idiopathic short stature. Rare genetic defects in the GH/IGF-1 axis have been found to cause short stature. OBJECTIVE: The objective of this study was to identify the genetic etiology of short stature in a patient with Idiopathic Short Stature and to review the clinical presentation of patients with genetic defects in IGF1, and specifically IGF-1 haploinsufficiency. DESIGN/SETTING/PARTICIPANTS: The index patient was evaluated at an academic medical center, and DNA was obtained from the proband and both parents. INTERVENTION: Genome-wide copy number analysis was performed in the proband with confirmatory quantitative PCR in the proband and his parents. MAIN OUTCOME MEASURE: We measured novel copy number variants (CNVs) thought to explain the patient's short stature. RESULTS: CNV analysis revealed that the proband carried a paternally inherited heterozygous IGF1 gene deletion. His phenotypic features are consistent with those found in previous case reports of IGF-1 deficiency. CONCLUSIONS: This study, as the first case of a complete heterozygous 1GF1 deletion, provides insight into the effects of true IGF-1 haploinsufficiency. Given the similarities in phenotype between the present proband and those previously described, it is highly likely that his IGF1 deletion is the cause for his short stature. Broadly, this study emphasizes how CNV analysis and other genetic sequencing techniques are evolving as an important tool to identify genetic causes underlying human disease, allowing for improved diagnosis and targeted treatment.

Pharmacotherapies for lipid modification: beyond the statins.

The widespread clinical use of statins has contributed to significant reductions in the rate of cardiovascular morbidity and mortality over the past 3 decades, and statins are considered first-line therapy for the prevention and treatment of atherosclerotic vascular disease. Nevertheless, various other lipid-lowering agents can provide clinical benefit by supplementing or augmenting statin therapy in patients with severe hypercholesterolaemia or mixed dyslipidaemia, or by providing an alternative for patients who are intolerant to statins. Bile acid resins and niacin were prescribed for lipid modification for years before the introduction of the statins, and new data continue to emerge regarding their use in different patient groups and for specific conditions. Ezetimibe can be appropriate for patients whose primary lipid abnormality is an elevated LDL-cholesterol level, whereas the fibrates seem to be most beneficial in patients with low levels of HDL cholesterol and elevated triglycerides. At the end of 2012 and the beginning of 2013, the first microsomal triglyceride transfer protein inhibitor, lomitapide, and the first antisense therapy to target apolipoprotein B, mipomersen, were approved for the treatment of individuals with extremely elevated LDL-cholesterol levels caused by homozygous familial hypercholesterolaemia. Although two agents in the experimental class of cholesteryl ester transfer protein inhibitors have failed to show a benefit in clinical trials, newer drugs in this class could provide an additional strategy to address residual cardiovascular risk in patients treated with statins.

An interstitial, apparently-balanced chromosomal insertion in the etiology of Langer-Giedion syndrome in an Asian family.

Langer-Giedion syndrome (LGS; MIM 150230), also called trichorhinophalangeal syndrome type II (TRPS2), is a contiguous gene syndrome caused by a one-copy deletion in the chromosome 8q23-q24 region, spanning the genes TRPS1 and EXT1. We identified an LGS family with two affected and two unaffected siblings from unaffected parents. To investigate the etiology of recurrence of LGS in this family, array CGH was performed on all family members. We identified a 7.29 Mb interstitial deletion at chromosome region 8q23-q24 in the two affected siblings, but no such deletion in the unaffected family members. However, the mother and one of the two unaffected siblings carried a 1.29 Mb deletion at chromosome region 8q24.1, sharing the distal breakpoint with the larger deleted segment found in the affected siblings. Another unaffected sibling had a 6.0 Mb duplication, sharing the proximal breakpoint of the deletion in the affected siblings. Karyotypic and FISH analyses in the unaffected mother revealed an insertional translocation of 8q23-q24 genomic material into chromosome 13: 46,XX,ins(13;8)(q33;q23q24). This insertional translocation in the mother results in the recurrence of LGS in this family, highlighting the importance of submicroscopic rearrangements in the genetic counseling for LGS.

Large-scale pooled next-generation sequencing of 1077 genes to identify genetic causes of short stature.

CONTEXT: The majority of patients presenting with short stature do not receive a definitive diagnosis. Advances in genetic sequencing allow for large-scale screening of candidate genes, potentially leading to genetic diagnoses. OBJECTIVES: The purpose of this study was to discover genetic variants that contribute to short stature in a cohort of children with no known genetic etiology. DESIGN: This was a prospective cohort study of subjects with short stature. SETTING: The setting was a pediatric endocrinology and genetics clinics at an academic center. PATIENTS: A total of 192 children with short stature with no defined genetic etiology and 192 individuals of normal stature from the Framingham Heart Study were studied. INTERVENTION: Pooled targeted sequencing using next-generation DNA sequencing technology of the exons of 1077 candidate genes was performed. MAIN OUTCOME MEASURES: The numbers of rare nonsynonymous genetic variants found in case patients but not in control subjects, known pathogenic variants in case patients, and potentially pathogenic variants in IGF1R were determined. RESULTS: We identified 4928 genetic variants in 1077 genes that were present in case patients but not in control subjects. Of those, 1349 variants were novel (898 nonsynonymous). False-positive rates from pooled sequencing were 4% to 5%, and the false-negative rate was 0.1% in regions covered well by sequencing. We identified 3 individuals with known pathogenic variants in PTPN11 causing undiagnosed Noonan syndrome. There were 9 rare potentially nonsynonymous variants in IGF1R, one of which is a novel, probably pathogenic, frameshift mutation. A previously reported pathogenic variant in IGF1R was present in a control subject. CONCLUSIONS: Large-scale sequencing efforts have the potential to rapidly identify genetic etiologies of short stature, but data interpretation is complex. Noonan syndrome may be an underdiagnosed cause of short stature.

Safety of inhibition of cholesteryl ester transfer protein with anacetrapib: the DEFINE study.

Inhibition of cholesteryl ester transfer protein is a strategy under investigation for raising HDL cholesterol levels and addressing residual cardiovascular risk after effective reduction of LDL cholesterol. In the Phase III DEFINE trial conducted in patients with or at high risk for coronary heart disease, anacetrapib reduced LDL cholesterol levels by 39.8% after 24 weeks compared with placebo and demonstrated an acceptable safety profile through 76 weeks of treatment (the primary end points). Anacetrapib caused a placebo-adjusted 138.1% increase in HDL cholesterol levels, with no alterations in blood pressure, aldosterone or electrolytes. The trial also provided reassurance that anacetrapib would not be associated with a 25% increase in cardiovascular events, as seen with a previous cholesteryl ester transfer protein inhibitor. Sustained effects on lipids were observed 12 weeks following cessation of anacetrapib treatment. Anacetrapib is being evaluated in an ongoing cardiovascular outcomes trial.

Novel microcephalic primordial dwarfism disorder associated with variants in the centrosomal protein ninein.

CONTEXT: Microcephalic primordial dwarfism (MPD) is a rare, severe form of human growth failure in which growth restriction is evident in utero and continues into postnatal life. Single causative gene defects have been identified in a number of patients with MPD, and all involve genes fundamental to cellular processes including centrosome functions. OBJECTIVE: The objective of the study was to find the genetic etiology of a novel presentation of MPD. DESIGN: The design of the study was whole-exome sequencing performed on two affected sisters in a single family. Molecular and functional studies of a candidate gene were performed using patient-derived primary fibroblasts and a zebrafish morpholino oligonucleotides knockdown model. PATIENTS: Two sisters presented with a novel subtype of MPD, including severe intellectual disabilities. MAIN OUTCOME MEASURES: NIN, encoding Ninein, a centrosomal protein critically involved in asymmetric cell division, was identified as a candidate gene, and functional impacts in fibroblasts and zebrafish were studied. RESULTS: From 34,606 genomic variants, two very rare missense variants in NIN were identified. Both probands were compound heterozygotes. In the zebrafish, ninein knockdown led to specific and novel defects in the specification and morphogenesis of the anterior neuroectoderm, resulting in a deformity of the developing cranium with a small, squared skull highly reminiscent of the human phenotype. CONCLUSION: We identified a novel clinical subtype of MPD in two sisters who have rare variants in NIN. We show, for the first time, that reduction of ninein function in the developing zebrafish leads to specific deficiencies of brain and skull development, offering a developmental basis for the myriad phenotypes in our patients.

Recent clinical studies of the effects of lipid-modifying therapies.

Results from multiple clinical trials, primarily with the class of lipid-lowering agents known as statins, have shown that reductions in low-density lipoprotein (LDL) cholesterol are associated with reduced risk of coronary artery disease. Although LDL cholesterol is the primary target of cholesterol management strategies, increasing attention has focused on the role of inflammation, high-density lipoprotein cholesterol, and triglycerides in atherosclerosis and cardiovascular disease. We review major trials with lipid-modifying therapies published since the 2004 update of the Adult Treatment Panel (ATP) III guidelines. A pivotal trial was the Justification for the Use of Statins in Primary Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER), which demonstrated significant reductions in cardiovascular morbidity and mortality in healthy individuals without elevated LDL cholesterol but with high levels of the inflammatory marker high-sensitivity C-reactive protein. Additional trials demonstrated the efficacy of intensive statin therapy in secondary prevention, whereas other agents, including fibrates, omega-3 fatty acids, niacin, ezetimibe, and experimental cholesteryl ester transfer protein inhibitors, have been evaluated for their ability to reduce residual cardiovascular risk.

Management of cardiovascular risk: the importance of meeting lipid targets.

Strategies to reduce cardiovascular risk in primary and secondary prevention focus on optimization of low-density lipoprotein (LDL) cholesterol levels. Since the 2004 update of the Adult Treatment Panel (ATP) III guidelines, developments in the field of preventive cardiology have included new guidelines for women and for familial hypercholesterolemia; a risk assessment algorithm incorporating the inflammatory marker high-sensitivity C-reactive protein (hsCRP); and clinical trial data confirming the efficacy of aggressive lipid management. Within secondary prevention in particular, there is a need for more widespread use of intensive statin therapy to achieve low LDL cholesterol levels to reduce cardiovascular morbidity and mortality in patients at high risk for recurrent events. Within primary prevention, individuals with diabetes mellitus, mixed dyslipidemia, or elevated hsCRP also are at increased risk and may warrant treatment with aggressive lipid-modifying therapy. In this article, we provide an update on recent guidelines, risk algorithms, and trials related to the prevention and treatment of coronary artery disease.