[Show abstract][Hide abstract] ABSTRACT: Sim1 is a bHLH-PAS transcription factor that is important for neuronal development in the hypothalamus. Loss-of-function mutation of Sim1 causes early onset obesity. However, it is unknown whether and how Sim1 regulates bone remodeling. In this study, we found that adult-onset Sim1 deletion increases bone formation, leading to high bone mass. In contrast, Sim1 over-expressing transgenic mice exhibit decreased bone formation and low bone mass. Sim1 does not directly regulate osteoblastogenesis because bone marrow mesenchymal stem cells from Sim1 mutant mice display a normal capacity for osteoblast differentiation. Instead, Sim1 inhibits bone formation via stimulating the sympathetic nervous system because sympathetic tone is decreased by Sim1 deletion but increased by Sim1 overexpression. Treatment with the β-adrenergic agonist isoproterenol effectively reverses the high bone mass in Sim1 KO mice. These findings reveal Sim1 as a critical yet previously unrecognized modulator of skeletal homeostasis that functions through a central relay.
[Show abstract][Hide abstract] ABSTRACT: IntroductionThe male sex chromosome disorder 47,XYY syndrome (XYY) is associated with increased risk for social-emotional difficulties, attention deficit (ADHD), and autism spectrum disorders (ASD). We hypothesize that increased Y chromosome gene copy number in XYY leads to overexpression of Y-linked genes related to brain development and function, thereby increasing risk for these phenotypes.Methods
We measured expression in blood of two Y genes NLGN4Y and RPS4Y in 26 boys with XYY and 11 male controls and evaluated whether NLGN4Y expression correlates with anxiety, ADHD, depression, and autistic behaviors (from questionnaires) in boys with XYY.ResultsThe XYY cohort had increased risk of ASD behaviors on the Social Responsiveness Scale (SRS) and increased attention deficits on the Conners’ DSM-IV Inattention and Hyperactive scales. In contrast, there was no increase in reported symptoms of anxiety or depression by the XYY group. Peripheral expression of two Y genes in boys with XYY versus TD controls was increased two-fold in the XYY group. Results from the SRS Total and Autistic Mannerisms scales but not the attention, anxiety or depression measures correlated with peripheral expression of NLGN4Y in boys with XYY.Conclusions
Males with XYY have social phenotypes that include increased risk for autism related behaviors and ADHD. Expression of NLGN4Y, a gene that may be involved in synaptic function, is increased in boys with XYY, and the level of expression correlates with overall social responsiveness and autism symptoms. Thus, further investigation of NLGN4Y as a plausible ASD risk gene in XYY is warranted.
[Show abstract][Hide abstract] ABSTRACT: Germline haploinsufficiency of human or mouse Sim1 is associated with hyperphagic obesity. Sim1 encodes a transcription factor required for proper formation of the paraventricular (PVN), supraoptic, and anterior periventricular hypothalamic nuclei. Sim1 expression persists in these neurons in adult mice, raising the question of whether it plays a physiologic role in regulation of energy balance. We previously showed that Sim1 heterozygous mice had normal numbers of PVN neurons that were hyporesponsive to melanocortin 4 receptor agonism and showed reduced oxytocin expression. Furthermore, conditional postnatal neuronal inactivation of Sim1 also caused hyperphagic obesity and decreased hypothalamic oxytocin expression. PVN projections to the hindbrain, where oxytocin is thought to act to modulate satiety, were anatomically intact in both Sim1 heterozygous and conditional knockout mice. These experiments provided evidence that Sim1 functions in energy balance apart from its role in hypothalamic development but did not rule out effects of Sim1 deficiency on postnatal hypothalamic maturation. To address this possibility, we used a tamoxifen-inducible, neural-specific Cre transgene to conditionally inactivate Sim1 in adult mice with mature hypothalamic circuitry. Induced Sim1 inactivation caused increased food and water intake and decreased expression of PVN neuropeptides, especially oxytocin and vasopressin, with no change in energy expenditure. Sim1 expression was not required for survival of PVN neurons. The results corroborate previous evidence that Sim1 acts physiologically as well as developmentally to regulate body weight. Inducible knockout mice provide a system for studying Sim1's physiologic function in energy balance and identifying its relevant transcriptional targets in the hypothalamus.
[Show abstract][Hide abstract] ABSTRACT: Hyperphagia is a central feature of inherited disorders (e.g., Prader-Willi Syndrome) in which obesity is a primary phenotypic component. Hyperphagia may also contribute to obesity as observed in the general population, thus raising the potential importance of common underlying mechanisms and treatments. Substantial gaps in understanding the molecular basis of inherited hyperphagia syndromes are present as are a lack of mechanistic of mechanistic targets that can serve as a basis for pharmacologic and behavioral treatments.
International conference with 28 experts, including scientists and caregivers, providing presentations, panel discussions, and debates.
The reviewed collective research and clinical experience provides a critical body of new and novel information on hyperphagia at levels ranging from molecular to population. Gaps in understanding and tools needed for additional research were identified.
This report documents the full scope of important topics reviewed at a comprehensive international meeting devoted to the topic of hyperphagia and identifies key areas for future funding and research.
[Show abstract][Hide abstract] ABSTRACT: To contrast the behavioral and social phenotypes including a screen for autistic behaviors in boys with 47,XYY syndrome (XYY) or 47,XXY Klinefelter syndrome (KS) and controls and investigate the effect of prenatal diagnosis on the phenotype.
Patients included 26 boys with 47,XYY, 82 boys with KS, and 50 control boys (ages 4-15 years). Participants and parents completed a physical examination, behavioral questionnaires, and intellectual assessments.
Most boys with XYY or KS had Child Behavior Checklist parental ratings within the normal range. On the Child Behavior Checklist, mean problem behaviors t scores were higher in the XYY versus KS groups for the Problem Behavior, Externalizing, Withdrawn, Thought Problems, and Attention Problems subscales. On the Conners' Parent Rating Scale-Revised, the XYY versus KS group had increased frequency of hyperactive/impulsive symptoms (P < .006). In addition, 50% and 12% of the XYY and KS groups, respectively, had scores >15 for autism screening from the Social Communication Questionnaire. For the boys with KS, prenatal diagnosis was associated with fewer problem behaviors.
A subset of the XYY and KS groups had behavioral difficulties that were more severe in the XYY group. These findings could guide clinical practice and inform patients and parents. Boys diagnosed with XYY or KS should receive a comprehensive psychoeducational evaluation and be screened for learning disabilities, attention-deficit/hyperactivity disorder, and autism spectrum disorders.
[Show abstract][Hide abstract] ABSTRACT: Hypoplastic left heart syndrome (HLHS), one of the most severe types of congenital heart disease (CHD), results in significant morbidity and mortality despite surgical palliation. The etiology of HLHS is unknown, but evidence supports genetic contributors. The authors hypothesized that submicroscopic chromosomal abnormalities exist in individuals with HLHS and are more frequent in those with additional birth defects. This study sought to determine the incidence and genomic location of submicroscopic chromosomal abnormalities in HLHS and potentially to identify novel genetic loci that may contribute to the disease. For this study, 43 children with HLHS were recruited and screened together with a control population of 16 subjects using array comparative genomic hybridization, also called chromosomal microarray, for chromosomal copy number variations (CNVs). A statistically greater number of CNVs were found in the HLHS group than in the control group (p < 0.03). The CNVs were predominantly small autosomal deletions and duplications (≤ 60,000 bp). The frequency of unique CNVs, those not previously reported in public databases, did not differ statistically between the HLHS subjects and the control subjects. No difference in the frequency of CNVs was noted between the patients with HLHS and additional anomalies and those with isolated HLHS. The identified CNVs did not harbor potential candidate genes for HLHS, but one microdeletion was located on chromosome 14q23, a genetic locus linked to left-sided CHD. The study data demonstrate that CNVs, specifically those relatively small in size, are more common in subjects with HLHS, but the frequency of large potentially disease-causing CNVs (>480,000 bp) did not differ between the HLHS and control populations.
[Show abstract][Hide abstract] ABSTRACT: Léri-Weill dyschondrosteosis (LWD) is a skeletal dysplasia characterized by disproportionate short stature and the Madelung deformity of the forearm. SHOX mutations and pseudoautosomal region 1 deletions encompassing SHOX or its enhancers have been identified in approximately 60% of LWD and approximately 15% of idiopathic short stature (ISS) individuals. Recently SHOX duplications have been described in LWD/ISS but also in individuals with other clinical manifestations, thus questioning their pathogenicity.
The objective of the study was to investigate the pathogenicity of SHOX duplications in LWD and ISS.
Multiplex ligation-dependent probe amplification is routinely used in our unit to analyze for SHOX/pseudoautosomal region 1 copy number changes in LWD/ISS referrals. Quantitative PCR, microsatellite marker, and fluorescence in situ hybridization analysis were undertaken to confirm all identified duplications.
During the routine analysis of 122 LWD and 613 ISS referrals, a total of four complete and 10 partial SHOX duplications or multiple copy number (n > 3) as well as one duplication of the SHOX 5' flanking region were identified in nine LWD and six ISS cases. Partial SHOX duplications appeared to have a more deleterious effect on skeletal dysplasia and height gain than complete SHOX duplications. Importantly, no increase in SHOX copy number was identified in 340 individuals with normal stature or 104 overgrowth referrals.
MLPA analysis of SHOX/PAR1 led to the identification of partial and complete SHOX duplications or multiple copies associated with LWD or ISS, suggesting that they may represent an additional class of mutations implicated in the molecular etiology of these clinical entities.
The Journal of Clinical Endocrinology and Metabolism 02/2011; 96(2):E404-12. DOI:10.1210/jc.2010-1689 · 6.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We studied a man with distal hypospadias, partial anomalous pulmonary venous return, mild limb-length inequality and a balanced translocation involving chromosomes 9 and 13. To gain insight into the etiology of his birth defects, we mapped the translocation breakpoints by high-resolution comparative genomic hybridization (CGH), using chromosome 9- and 13-specific tiling arrays to analyze genetic material from a spontaneously aborted fetus with unbalanced segregation of the translocation. The chromosome 13 breakpoint was ∼400 kb away from the nearest gene, but the chromosome 9 breakpoint fell within an intron of Basonuclin 2 (BNC2), a gene that encodes an evolutionarily conserved nuclear zinc-finger protein. The BNC2/Bnc2 gene is abundantly expressed in developing mouse and human periurethral tissues. In all, 6 of 48 unrelated subjects with distal hypospadias had nine novel nonsynonymous substitutions in BNC2, five of which were computationally predicted to be deleterious. In comparison, two of 23 controls with normal penile urethra morphology, each had a novel nonsynonymous substitution in BNC2, one of which was predicted to be deleterious. Bnc2(-/-) mice of both sexes displayed a high frequency of distal urethral defects; heterozygotes showed similar defects with reduced penetrance. The association of BNC2 disruption with distal urethral defects and the gene's expression pattern indicate that it functions in urethral development.
European journal of human genetics: EJHG 02/2011; 19(5):540-6. DOI:10.1038/ejhg.2010.245 · 4.35 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe three patients with a comparable deletion encompassing SLC25A43, SLC25A5, CXorf56, UBE2A, NKRF, and two non-coding RNA genes, U1 and LOC100303728. Moderate to severe intellectual disability (ID), psychomotor retardation, severely impaired/absent speech, seizures, and urogenital anomalies were present in all three patients. Facial dysmorphisms include ocular hypertelorism, synophrys, and a depressed nasal bridge. These clinical features overlap with those described in two patients from a family with a similar deletion at Xq24 that also includes UBE2A, and in several patients of Brazilian and Polish families with point mutations in UBE2A. Notably, all five patients with an Xq24 deletion have ventricular septal defects that are not present in patients with a point mutation, which might be attributed to the deletion of SLC25A5. Taken together, the UBE2A deficiency syndrome in male patients with a mutation in or a deletion of UBE2A is characterized by ID, absent speech, seizures, urogenital anomalies, frequently including a small penis, and skin abnormalities, which include generalized hirsutism, low posterior hairline, myxedematous appearance, widely spaced nipples, and hair whorls. Facial dysmorphisms include a wide face, a depressed nasal bridge, a large mouth with downturned corners, thin vermilion, and a short, broad neck.
American Journal of Medical Genetics Part A 12/2010; 152A(12):3084-90. DOI:10.1002/ajmg.a.33743 · 2.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Diet and sedentary lifestyle, interacting with "thrifty" genes, are widely accepted as the principal cause of the current global obesity epidemic. However, a number of alternative etiologies for obesity have been proposed, including "drifty" genes, viruses, bacteria, environmental toxins, social network effects, maternal imprinting, sleep deprivation, and others. These Grand Rounds reviews the background of some of these unconventional ideas and evidence for or against their roles in the obesity epidemic.
The American Journal of the Medical Sciences 12/2010; 340(6):481-91. DOI:10.1097/MAJ.0b013e3181ccb980 · 1.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: PKC-theta (PKC-θ), a member of the novel protein kinase C family (nPKC), regulates a wide variety of functions in the periphery. However, its presence and role in the CNS has remained largely unknown. Recently, we demonstrated the presence of PKC-θ in the arcuate hypothalamic nucleus (ARC) and knockdown of PKC-θ from the ARC protected mice from developing diet-induced obesity. Another isoform of the nPKC group, PKC-delta (PKC-δ), is expressed in several non-hypothalamic brain sites including the thalamus and hippocampus. Although PKC-δ has been implicated in regulating hypothalamic glucose homeostasis, its distribution in the hypothalamus has not previously been described. In the current study, we used immunohistochemistry to examine the distribution of PKC-θ and -δ immunoreactivity in rat and mouse hypothalamus. We found PKC-θ immunoreactive neurons in several hypothalamic nuclei including the ARC, lateral hypothalamic area, perifornical area and tuberomammillary nucleus. PKC-δ immunoreactive neurons were found in the paraventricular and supraoptic nuclei. Double-label immunohistochemisty in mice expressing green fluorescent protein either with the long form of leptin receptor (LepR-b) or in orexin (ORX) neurons indicated that PKC-θ is highly colocalized in lateral hypothalamic ORX neurons but not in lateral hypothalamic LepR-b neurons. Double-label immunohistochemistry in oxytocin-enhanced yellow fluorescent protein mice or arginine vasopressin-enhanced green fluorescent protein (AVP-EGFP) transgenic rats revealed a high degree of colocalization of PKC-δ within paraventricular and supraoptic oxytocin neurons but not the vasopressinergic neurons. We conclude that PKC-θ and -δ are expressed in different hypothalamic neuronal populations.
[Show abstract][Hide abstract] ABSTRACT: D-Fenfluramine (D-Fen) increases serotonin (5-HT) content in the synaptic cleft and exerts anorexigenic effects in animals and humans. However, the neural circuits that mediate these effects are not fully identified. To address this issue, we assessed the efficacy of D-Fen-induced hypophagia in mouse models with manipulations of several genes in selective populations of neurons. Expectedly, we found that global deletion of 5-HT 2C receptors (5-HT(2C)Rs) significantly attenuated D-Fen-induced anorexia. These anorexigenic effects were restored in mice with 5-HT(2C)Rs expressed only in pro-opiomelanocortin (POMC) neurons. Further, we found that deletion of melanocortin 4 receptors (MC4Rs), a downstream target of POMC neurons, abolished anorexigenic effects of D-Fen. Reexpression of MC4Rs only in SIM1 neurons in the hypothalamic paraventricular nucleus and neurons in the amygdala was sufficient to restore the hypophagic property of D-Fen. Thus, our results identify a neurochemically defined neural circuit through which D-Fen influences appetite and thereby indicate that this 5-HT(2C)R/POMC-MC4R/SIM1 circuit may yield a more refined target to exploit for weight loss.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 11/2010; 30(44):14630-4. DOI:10.1523/JNEUROSCI.5412-09.2010 · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Single-minded 1 (SIM1) mutations are one of the few known causes of nonsyndromic monogenic obesity in both humans and mice. Although the role of Sim1 in the formation of the hypothalamus has been described, its postdevelopmental, physiological functions have not been well established. Here we demonstrate that postnatal CNS deficiency of Sim1 is sufficient to cause hyperphagic obesity. We conditionally deleted Sim1 after birth using CaMKII-Cre (alpha-calcium/calmodulin-dependent protein kinase II-Cre) lines to recombine a floxed Sim1 allele. Conditional Sim1 heterozygotes phenocopied germ line Sim1 heterozygotes, displaying hyperphagic obesity and increased length. We also generated viable conditional Sim1 homozygotes, demonstrating that adult Sim1 expression is not essential for mouse or neuron survival and revealing a dosage-dependent effect of Sim1 on obesity. Using stereological cell counting, we showed that the phenotype of both germ line heterozygotes and conditional Sim1 homozygotes was not attributable to global hypocellularity of the paraventricular nucleus (PVN) of the hypothalamus. We also used retrograde tract tracing to demonstrate that the PVN of germ line heterozygous mice projects normally to the dorsal vagal complex and the median eminence. Finally, we showed that conditional Sim1 homozygotes and germ line Sim1 heterozygotes exhibit a remarkable decrease in hypothalamic oxytocin (Oxt) and PVN melanocortin 4 receptor (Mc4r) mRNA. These results demonstrate that the role of Sim1 in feeding regulation is not limited to formation of the PVN or its projections and that the hyperphagic obesity in Sim1-deficient mice may be attributable to changes in the leptin-melanocortin-oxytocin pathway.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 03/2010; 30(10):3803-12. DOI:10.1523/JNEUROSCI.5444-09.2010 · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Purpose: VACTERL (Vertebral, Anorectal, Cardiac, TracheoEsophageal, Renal, or Limb) association is the non-random co-occurrence of 2-3 of 7 congenital defects affecting 1 in 5000 live births. These anomalies can be devastating psychologically, financially, socially, and medically for the child and family. Despite its frequency, the cause(s) of VACTERL is poorly understood, but occasionally karyotypic anomalies have been reported. Given the recent advances in molecular medicine, we screened a population of VACTERL patients with the more sensitive whole genome microarray comparative genomic hybridization (CGH) for genomic alterations.
Methods: Using IRB-approved protocols, severely affected VACTERL patients (three or more defects) and willing family members were recruited. Detailed phenotypic information was obtained from medical records. Peripheral blood was obtained for blood lymphocyte immortalization and high quality DNA extraction. Whole genome microarray CGH was performed per protocol with unaffected patient samples serving as controls. On average, the oligonucleotide probes were spaced every 6000bp throughout the entire nonrepetitive portion of the human genome.
Results: From 2002-2008, 43 VACTERL patients were recruited. 36 (83.7%) were screened by microarray CGH, with 12 having positive findings. Of these 12 patients, 6 had results thought to be of potential significance. One male patient had partial trisomy 22 resulting in a polygenic duplication which has previously been reported to cause VACTERL and Der(22) syndrome. Four patients had: (1) a homozygous microdeletion of a single gene on chromosome 11, (2) a microduplication on chromosome 8 involving 3 known genes, (3) a microduplication of a region of chromosome 18 encompassing 2 known genes, and (4) a microdeletion of a single gene in chromosome 15 and a microduplication of 2 genes in chromosome 7 respectively. The remaining patient had a polygenic mutation comprised of a chromosome 12 deletion and a chromosome 16 duplication.
Conclusion: Genomic alterations were detected in 34% of our severely affected VACTERL patients via array CGH. Further study of each of these chromosomal alterations may lead to the identification of causal genes, thereby leading to mechanistic insight in VACTERL pathogenesis.
2009 American Academy of Pediatrics National Conference and Exhibition; 10/2009
[Show abstract][Hide abstract] ABSTRACT: Purpose: The causes of classic bladder exstrophy (CBE) remain unknown. Patients with focal dermal hypoplasia/Goltz Syndrome (FDH, OMIM #305600) have recently been reported to have mutations in the PORCN gene on chromosome Xp11.23. Having identified a patient with FDH and CBE, we hypothesized that PORCN may be implicated in the etiology of CBE. We screened a population of CBE patients for mutations in PORCN and performed a literature search for additional cases.
Methods: After patient recruitment, genomic DNA was isolated from lymphocytes. PORCN coding exons 1-11 from CBE patients were screened by directional PCR sequencing. In 59 normal control DNAs, identified PORCN mutations were screened for SNPs. X-chromosome microarray comparative genomic hybridization (aCGH, Nimblegen, Madison, WI) was performed on samples with identified PORCN mutations to assess for copy number variations. A PubMed literature search was performed for additional FDH cases screened for PORCN mutations, identifying FDH cases with CBE.
Results: 10 CBE patients (5M:5F) were screened for PORCN mutations, of which 3 had CBE only (1M:2F), 6 had CBE + additional congenital anomalies (4M:2F), and 1 had FDH + CBE (1F). A previously unreported novel heterozygous missense point mutation (W312R) was identified in our one female patient with FDH + CBE; X-chromosome-specific aCGH was negative for copy number variations.in this patient. No other mutations were detected. Literature search revealed three additional published female cases with FDH + CBE with point mutations (G60R, C385Y and W439X). Overall, we found CBE to be present in four of 73 (5.5%) FDH patients in which PORCN was sequenced.
Conclusion: : FDH and CBE are individually rare disorders, and their co-occurrence in at least four patients suggests etiological relatedness. Importantly, all 4 (100%) of these patients have PORCN muations. While PORCN genomic alterations are present in ~75% of FDH patients, we did not find PORCN mutations in the isolated cases of CBE, perhaps due to the small study group that also included males. PORCN governs WNT protein palmitoylation, a necessary step for WNT protein trafficking to the extracellular membrane. WNT genes are crucial for embryonic development; further study of WNT and PORCN genes may yield insight into molecular causes for CBE. Despite the lasck of mutations in our CBE cohort, PORCN remains a strong candidate gene for CBE and warrants further investigation.
2009 American Academy of Pediatrics National Conference and Exhibition; 10/2009
[Show abstract][Hide abstract] ABSTRACT: Homozygous mutation of the short stature homeobox-containing gene, SHOX, results in Langer mesomelic dysplasia (LMD). Our case presented with severe short stature and skeletal deformities with Turner syndrome (TS) and a SHOX gene abnormality due to a downstream allele deletion in her normal X chromosome. Medical literature review did not reveal similar cases that were treated with GH therapy.
We present an 11-yr-old with combined TS and LMD with severe short stature and skeletal deformities. She was studied for the effect of GH therapy on stature and skeletal deformities. Karyotype testing showed 45,X/46,X,idic(X). Genetic analysis of SHOX gene testing did not detect any exonic mutations. Interestingly, both alleles of the flanking marker DXYS233, a marker downstream of the 3' end of SHOX coding sequence, were absent with resultant LMD. GH therapy in the mean dose of 0.321 mg/kg/wk was administered for 4 yr (0.287, 0.355, 0.317, and 0.327 mg/kg/week in the first, second, third, and fourth years, respectively). Clinical data were reviewed.
The growth rates of 3.46, 3.87, 2.3, and 0.7 cm/yr were observed in the first, second, third, and fourth years of the GH therapy, respectively. There was no clinical deterioration of the skeletal deformities.
There was a failure to achieve growth improvements with GH therapy for 4 years, but there was no worsening of the skeletal deformities. We conclude that GH therapy may not be beneficial in severe short stature due to combined TS and LMD resulting from homozygous SHOX deficiency.
The Journal of Clinical Endocrinology and Metabolism 10/2009; 94(12):5028-33. DOI:10.1210/jc.2009-0679 · 6.21 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Statistical power calculations are a critical part of any study design for gene mapping. Most calculations assume that the locus of interest is biallelic. However, there are common situations in human genetics such as X-linked loci in males where the locus is haploid. The purpose of this work is to mathematically derive the biometric model for haploid loci, and to compute power for QTL mapping when the loci are haploid.
We have derived the biometric model for power calculations for haploid loci and have developed software to perform these calculations. We have verified our calculations with independent mathematical methods.
Our results fill a need in power calculations for QTL mapping studies. Furthermore, failure to appropriately model haploid loci may cause underestimation of power.