Exome Sequencing and High-Density Microarray Testing in Monozygotic Twin Pairs Discordant for Features of VACTERL Association.

Exome sequencing offers an efficient and affordable method to interrogate genetic factors involved in human disease. Performing exome sequencing of monozygotic twins discordant for VACTERL (Vertebral anomalies, Anal atresia, Cardiac malformations, Tracheo-Esophageal fistula, Renal anomalies, and Limb abnormalities) association-type congenital malformations was hypothesized to potentially reveal discordant variants that could demonstrate disease cause(s). After demonstrating monozygosity, we applied high-density microarrays and exome sequencing to 2 twin pairs in which 1 twin had features of VACTERL association while the other was phenotypically normal (demonstrated through comprehensive clinical and radiological evaluation). No obvious discordant genotypic results were found that would explain phenotypic discordance. We conclude that VACTERL association is a complex disease, and while performing microarray analysis and exome sequencing on phenotypically discordant monozygotic twins may hypothetically reveal genetic causes of disorders, challenges remain in applying these methods in this circumstance.

A cooperative interaction between LPHN3 and 11q doubles the risk for ADHD.

In previous studies of a genetic isolate, we identified significant linkage of attention deficit hyperactivity disorder (ADHD) to 4q, 5q, 8q, 11q and 17p. The existence of unique large size families linked to multiple regions, and the fact that these families came from an isolated population, we hypothesized that two-locus interaction contributions to ADHD were plausible. Several analytical models converged to show significant interaction between 4q and 11q (P<1 × 10(-8)) and 11q and 17p (P<1 × 10(-6)). As we have identified that common variants of the LPHN3 gene were responsible for the 4q linkage signal, we focused on 4q-11q interaction to determine that single-nucleotide polymorphisms (SNPs) harbored in the LPHN3 gene interact with SNPs spanning the 11q region that contains DRD2 and NCAM1 genes, to double the risk of developing ADHD. This interaction not only explains genetic effects much better than taking each of these loci effects by separated but also differences in brain metabolism as depicted by proton magnetic resonance spectroscopy data and pharmacogenetic response to stimulant medication. These findings not only add information about how high order genetic interactions might be implicated in conferring susceptibility to develop ADHD but also show that future studies of the effects of genetic interactions on ADHD clinical information will help to shape predictive models of individual outcome.

A Hypomorphic Allele in the FGF8 Gene Contributes to Holoprosencephaly and Is Allelic to Gonadotropin-Releasing Hormone Deficiency in Humans.

Holoprosencephaly (HPE), the most common malformation of the human forebrain, may arise due to interacting genetic and environmental factors. To date, at least 12 contributory genes have been identified. Fibroblast growth factor 8 (Fgf8) belongs to the FGF family of genes expressed in several developmental signaling centers, including the anterior neural ridge, which is implicated in midline anomalies in mice. In humans, FGF8 mutations have been previously reported in facial clefting and in hypogonadotropic hypogonadism, but have not been reported in patients with HPE. We screened 360 probands with HPE for sequence variations in FGF8 using High Resolution DNA Melting (HRM) and sequenced all identified variations. Here we describe a total of 8 sequence variations in HPE patients, including a putative loss-of-function mutation in 3 members of a family with variable forms of classic HPE, and relate these findings to the phenotypes seen in other conditions.

Everolimus versus azathioprine in a cyclosporine and ketoconazole-based immunosuppressive therapy in kidney transplant: 3-year follow-up of an open-label, prospective, cohort, comparative clinical trial.

In cyclosporine-based protocols, everolimus is more effective than azathioprine to reduce acute rejection. Ketoconazole may reduce cyclosporine and everolimus requirements. We compared kidney transplant patients treated with everolimus or azathioprine in a ketoconazole- and cyclosporine-based immunosuppressive regimen. This open-label, prospective trial of low immunologic risk patients. Included one group (n = 11) who received everolimus (target blood level, 3-8 ng/mL) and the other (n = 11) azathioprine (2.0-2.5 mg/kg/d). Both received steroids, ketoconazole, and cyclosporine with C(0) targets (ng/mL) in the everolimus group of 200-250, 100-125, and 50-65 for months 1 and 2 and thereafter and in the azathioprine group of 250-300 in month 1, 200-250 in month 2, 180-200 until month 6, and 100-125 thereafter. Their baseline characteristics were similar. Two biopsy-proven acute rejections occurred in each group. Three-year graft and patient survival in both groups was 100%. Creatinine clearances at months 6, 12, 24, and 36 were 63.7 +/- 25.4, 58.9 +/- 24.9, 56.0 +/- 22.9, and 57.0 +/- 27.6 in the everolimus group versus 72.6 +/- 20, 68.6 +/- 21.3, 71.4 +/- 23.2, and 68.4 +/- 19.2 in the azathioprine group (NS for every comparison). Major complications were rare and similar in both groups. Five patients in the everolimus group received simvastatin versus 4 in the azathioprine cohort (P = .53). The average cyclosporine doses to achieve targets were 0.8-1.2 mg/kg in the everolimus group and 1.6-2.2 mg/kg in the azathioprine group. The average everolimus dose after month 2 was 0.75-0.9 mg/d. We concluded that with cyclosporine, ketoconazole, and steroids, everolimus was as effective and safe as azathioprine. Cyclosporine reduction with everolimus did not influence graft survival or function at 3 years.

Effectiveness and cost of replacing a calcineurin inhibitor with sirolimus to slow the course of chronic kidney disease in renal allografts.

Renal grafts suffer a progressive decrease in glomerular filtration rate (GFR) because of several factors including calcineurin inhibitor (CNI) nephrotoxicity. Switching CNIs to sirolimus may improve this adverse prognosis. We performed a prospective, open-label clinical trial among 18 kidney transplant patients with more than 12 months of evolution (range, 385-1826 days), showing progressive GFR decreases and biopsies with interstitial fibrosis and tubular atrophy (IFTA). Immunosuppressive treatment included cyclosporine, ketoconazole, and steroids associated with azathioprine or mycophenolate mofetil. After signing an Institutional Review Board-approved written consent, cyclosporine was switched to sirolimus seeking to achieve a trough blood sirolimus concentration of 6-15 ng/mL. Wilcoxon and Student's t-tests were used to compare the values in the annual periods before and after the switch. GFR was estimated by the Modification of Diet in Renal Disease formula. There were no acute rejection episodes. Estimated GFR on the day of the switch was 38.0 +/- 12.1 mL/min. After CNI switch, the slope of the estimated GFR significantly improved from -6.5 +/- 9.2 to 8.1 +/- 14.0 mL/min/year (P < .01). The estimated GFR 1 year after the switch was 47.2 +/- 16.9 mL/min (P = .003 vs baseline). Total expenditures increased. The ratio of post-switch versus baseline total expenditures was 1.93 (95% confidence interval, 1.54-2.31) and the ratio of sirolimus to CNI cost was 2.16 (95% confidence interval, 1.53-2.78). Switching from CNI to sirolimus for kidney transplants with decreasing GFR and a biopsy with IFTA changes, suggesting progressive graft nephropathy, almost doubled total expenses. It is necessary to conduct trials using clinical end points to definitively validate this therapeutic intervention.

A common variant of the latrophilin 3 gene, LPHN3, confers susceptibility to ADHD and predicts effectiveness of stimulant medication.

Attention-Deficit/Hyperactivity Disorder (ADHD) has a very high heritability (0.8), suggesting that about 80% of phenotypic variance is due to genetic factors. We used the integration of statistical and functional approaches to discover a novel gene that contributes to ADHD. For our statistical approach, we started with a linkage study based on large multigenerational families in a population isolate, followed by fine mapping of targeted regions using a family-based design. Family- and population-based association studies in five samples from disparate regions of the world were used for replication. Brain imaging studies were performed to evaluate gene function. The linkage study discovered a genome region harbored in the Latrophilin 3 gene (LPHN3). In the world-wide samples (total n=6360, with 2627 ADHD cases and 2531 controls) statistical association of LPHN3 and ADHD was confirmed. Functional studies revealed that LPHN3 variants are expressed in key brain regions related to attention and activity, affect metabolism in neural circuits implicated in ADHD, and are associated with response to stimulant medication. Linkage and replicated association of ADHD with a novel non-candidate gene (LPHN3) provide new insights into the genetics, neurobiology, and treatment of ADHD.

TGIF Mutations in Human Holoprosencephaly: Correlation between Genotype and Phenotype.

Holoprosencephaly (HPE), which results from failed or incomplete midline forebrain division early in gestation, is the most common forebrain malformation. The etiology of HPE is complex and multifactorial. To date, at least 12 HPE-associated genes have been identified, including TGIF (transforming growth factor beta-induced factor), located on chromosome 18p11.3. TGIF encodes a transcriptional repressor of retinoid responses involved in TGF-ß signaling regulation, including Nodal signaling. TGIF mutations are reported in approximately 1-2% of patients with non-syndromic, non-chromosomal HPE. We combined data from our comprehensive studies of HPE with a literature search for all individuals with HPE and evidence of mutations affecting TGIF in order to establish the genotypic and phenotypic range. We describe 2 groups of patients: 34 with intragenic mutations and 21 with deletions of TGIF. These individuals, which were ascertained from our research group, in collaboration with other centers, and through a literature search, include 38 probands and 17 mutation-positive relatives. The majority of intragenic mutations occur in the TGIF homeodomain. Patients with mutations affecting TGIFrecapitulate the entire phenotypic spectrum observed in non-chromosomal, non-syndromic HPE. We identified a statistically significant difference between the 2 groups with respect to inheritance, as TGIF deletions were more likely to be de novo in comparison to TGIF mutations (χ(2) ((2)) = 6.97, p(permutated) = 0.0356). In addition, patients with TGIF deletions were also found to more commonly present with manifestations beyond the craniofacial and neuroanatomical features associated with HPE (p = 0.0030). These findings highlight differences in patients with intragenic mutations versus deletions affecting TGIF, and draw attention to the homeodomain region, which appears to be particularly relevant to HPE. These results may be useful for genetic counseling of affected patients.

Clinical spectrum of SIX3-associated mutations in holoprosencephaly: correlation between genotype, phenotype and function.

BACKGROUND: Holoprosencephaly (HPE) is the most common structural malformation of the human forebrain. There are several important HPE mutational target genes, including the transcription factor SIX3, which encodes an early regulator of Shh, Wnt, Bmp and Nodal signalling expressed in the developing forebrain and eyes of all vertebrates. OBJECTIVE: To characterise genetic and clinical findings in patients with SIX3 mutations. METHODS: Patients with HPE and their family members were tested for mutations in HPE-associated genes and the genetic and clinical findings, including those for additional cases found in the literature, were analysed. The results were correlated with a mutation-specific functional assay in zebrafish. RESULTS: In a cohort of patients (n = 800) with HPE, SIX3 mutations were found in 4.7% of probands and additional cases were found through testing of relatives. In total, 138 cases of HPE were identified, 59 of whom had not previously been clinically presented. Mutations in SIX3 result in more severe HPE than in other cases of non-chromosomal, non-syndromic HPE. An over-representation of severe HPE was found in patients whose mutations confer greater loss of function, as measured by the functional zebrafish assay. The gender ratio in this combined set of patients was 1.5:1 (F:M) and maternal inheritance was almost twice as common as paternal. About 14% of SIX3 mutations in probands occur de novo. There is a wide intrafamilial clinical range of features and classical penetrance is estimated to be at least 62%. CONCLUSIONS: Our data suggest that SIX3 mutations result in relatively severe HPE and that there is a genotype-phenotype correlation, as shown by functional studies using animal models.

Loss-of-function mutations in growth differentiation factor-1 (GDF1) are associated with congenital heart defects in humans.

Congenital heart defects (CHDs) are among the most common birth defects in humans (incidence 8-10 per 1,000 live births). Although their etiology is often poorly understood, most are considered to arise from multifactorial influences, including environmental and genetic components, as well as from less common syndromic forms. We hypothesized that disturbances in left-right patterning could contribute to the pathogenesis of selected cardiac defects by interfering with the extrinsic cues leading to the proper looping and vessel remodeling of the normally asymmetrically developed heart and vessels. Here, we show that heterozygous loss-of-function mutations in the human GDF1 gene contribute to cardiac defects ranging from tetralogy of Fallot to transposition of the great arteries and that decreased TGF- beta signaling provides a framework for understanding their pathogenesis. These findings implicate perturbations of the TGF- beta signaling pathway in the causation of a major subclass of human CHDs.

Impact of pregnancy on the function of transplanted kidneys.

INTRODUCTION: This study reviewed the course of pregnancies in terms of impact on renal function and delivery-related data among women who received kidney transplants in our unit. METHODS: We reviewed the medical records of women transplanted between 1982 and 2002 who became pregnant. We recorded the data of medical, obstetrical, and transplant-related complications, plasma creatinine levels, and blood pressures at baseline, delivery, and 12 months after delivery. RESULTS: Thirty women had 37 pregnancies. Immunosuppressive protocols included cyclosporine, ketoconazole, azathioprine, and prednisone in 22 patients or azathioprine and prednisone in 15. Renal function decreased significantly: mean creatinine levels at baseline, delivery, and after 1 year were: 1.19 +/- 0.38 mg/dL; 1.44 +/- 0.70 mg/dL; and 1.38 +/- 0.53 mg/dL, respectively (P = .023 and P = .004 vs baseline respectively). Systolic and diastolic blood pressures at delivery were higher than at baseline (134 +/- 19 and 86 +/- 14 mm Hg vs 126 +/- 21 and 79 +/- 13 mm Hg (P = .029 and P = .053, respectively). These values normalized 1 year later (128 +/- 21 and 80 +/- 16). Decreased use of antihypertensive drugs were the cause of poor blood pressure control (1.8 +/- 1.3 vs 0.9 +/- 0.7, P < .01). Blood pressure control improved following delivery. The most frequent complications were preeclampsia (18.9%), intrahepatic cholestasis (13.5%), and urinary tract infections (13.5%). There were five rejection episodes. Seven miscarriages took place and one mole. Eleven pregnancies were uncomplicated. CONCLUSION: Renal transplantation is the best treatment for fertile women with end-stage renal disease who want to become pregnant. However, pregnancy is risky for the mother, fetus, newborn, and allograft.

The genomic structure, chromosomal localization, and analysis of SIL as a candidate gene for holoprosencephaly.

Holoprosencephaly (HPE) is the most common congenital malformation of the brain and face in humans. In this study we report the analysis of SIL (Sumacr;CL iumacr;nterrupting lumacr;ocus) as a candidate gene for HPE. Fluorescent in situ hybridization (FISH) analysis using a BAC 246e16 confirmed the assignment of SIL to 1p32. Computational analysis of SIL at the protein level revealed a 73% overall identity between the human and murine proteins. Denaturing high performance liquid chromatography (dHPLC) techniques were used to screen for mutations and these studies identified several common polymorphisms but no disease-associated mutations, suggesting that SIL is not a common factor in HPE pathogenesis in humans.

[Orbito-palpebral emphysema due to ethmoidal fracture]. / Orbito-palpebrales Emphysem bei Siebbeinfraktur nach Kopfprellung.

BACKGROUND: Orbito-palpebral emphysema is a frequent pathological entity due to head injury. We report on a patient and correlate the clinical view and computer tomography findings. CASE REPORT: A 17-year-old male was referred to our hospital after a blunt trauma to his head. Visual acuity was 1,0. Diplopia, restricted motility and exophthalmus about 4 mm were found. CONCLUSION: If swelling of the lid is found orbito-palpebral emphysema should be thought of to initiate appropriate therapy to avoid possible severe complications, for example, occlusion of the retinal central artery.

Midline and laterality defects: left and right meet in the middle.

The aim of this review is to summarize some of the recent advances in molecular embryology that help to explain the pathogenesis of holoprosencephaly (HPE), or its related malformation in model organisms, cyclopia, and laterality defects in humans, derived from detailed analysis of similar malformations in animal models. Recently, defects in several developmental pathways including those operated by the Sonic hedgehog and Nodal signaling factors have been implicated as causes of HPE or laterality defects in humans. Here we summarize the findings in animal models that indicate that both defects can be explained by mechanisms that relate to the proper development of the axial midline in vertebrates. Published 2001 John Wiley & Sons, Inc.

Reciprocal mouse and human limb phenotypes caused by gain- and loss-of-function mutations affecting Lmbr1.

The major locus for dominant preaxial polydactyly in humans has been mapped to 7q36. In mice the dominant Hemimelic extra toes (Hx) and Hammertoe (Hm) mutations map to a homologous chromosomal region and cause similar limb defects. The Lmbr1 gene is entirely within the small critical intervals recently defined for both the mouse and human mutations and is misexpressed at the exact time that the mouse Hx phenotype becomes apparent during limb development. This result suggests that Lmbr1 may underlie preaxial polydactyly in both mice and humans. We have used deletion chromosomes to demonstrate that the dominant mouse and human limb defects arise from gain-of-function mutations and not from haploinsufficiency. Furthermore, we created a loss-of-function mutation in the mouse Lmbr1 gene that causes digit number reduction (oligodactyly) on its own and in trans to a deletion chromosome. The loss of digits that we observed in mice with reduced Lmbr1 activity is in contrast to the gain of digits observed in Hx mice and human polydactyly patients. Our results suggest that the Lmbr1 gene is required for limb formation and that reciprocal changes in levels of Lmbr1 activity can lead to either increases or decreases in the number of digits in the vertebrate limb.

Loss-of-function mutations in the EGF-CFC gene CFC1 are associated with human left-right laterality defects.

All vertebrates display a characteristic asymmetry of internal organs with the cardiac apex, stomach and spleen towards the left, and the liver and gall bladder on the right. Left-right (L-R) axis abnormalities or laterality defects are common in humans (1 in 8,500 live births). Several genes (such as Nodal, Ebaf and Pitx2) have been implicated in L-R organ positioning in model organisms. In humans, relatively few genes have been associated with a small percentage of human situs defects. These include ZIC3 (ref. 5), LEFTB (formerly LEFTY2; ref. 6) and ACVR2B (encoding activin receptor IIB; ref. 7). The EGF-CFC genes, mouse Cfc1 (encoding the Cryptic protein; ref. 9) and zebrafish one-eyed pinhead (oep; refs 10, 11) are essential for the establishment of the L-R axis. EGF-CFC proteins act as co-factors for Nodal-related signals, which have also been implicated in L-R axis development. Here we identify loss-of-function mutations in human CFC1 (encoding the CRYPTIC protein) in patients with heterotaxic phenotypes (randomized organ positioning). The mutant proteins have aberrant cellular localization in transfected cells and are functionally defective in a zebrafish oep-mutant rescue assay. Our findings indicate that the essential role of EGF-CFC genes and Nodal signalling in left-right axis formation is conserved from fish to humans. Moreover, our results support a role for environmental and/or genetic modifiers in determining the ultimate phenotype in humans.

The genomic structure, chromosome location, and analysis of the human DKK1 head inducer gene as a candidate for holoprosencephaly.

Holoprosencephaly (HPE) is the most common developmental defect of the brain and face in humans. Here we report the analysis of the human ortholog of dkk-1 as a candidate gene for HPE. We determined the genomic structure of the human gene DKK1 and mapped it to chromosome 10q11.2. Functional analysis of four missense mutations identified in HPE patients revealed preserved activity in head induction assays in frogs suggesting a limited role for this gene in HPE pathogenesis.

Mutations in TGIF cause holoprosencephaly and link NODAL signalling to human neural axis determination.

Holoprosencephaly (HPE) is the most common structural defect of the developing forebrain in humans (1 in 250 conceptuses, 1 in 16,000 live-born infants). HPE is aetiologically heterogeneous, with both environmental and genetic causes. So far, three human HPE genes are known: SHH at chromosome region 7q36 (ref. 6); ZIC2 at 13q32 (ref. 7); and SIX3 at 2p21 (ref. 8). In animal models, genes in the Nodal signalling pathway, such as those mutated in the zebrafish mutants cyclops (refs 9,10), squint (ref. 11) and one-eyed pinhead (oep; ref. 12), cause HPE. Mice heterozygous for null alleles of both Nodal and Smad2 have cyclopia. Here we describe the involvement of the TG-interacting factor (TGIF), a homeodomain protein, in human HPE. We mapped TGIF to the HPE minimal critical region in 18p11.3. Heterozygous mutations in individuals with HPE affect the transcriptional repression domain of TGIF, the DNA-binding domain or the domain that interacts with SMAD2. (The latter is an effector in the signalling pathway of the neural axis developmental factor NODAL, a member of the transforming growth factor-beta (TGF-beta) family.) Several of these mutations cause a loss of TGIF function. Thus, TGIF links the NODAL signalling pathway to the bifurcation of the human forebrain and the establishment of ventral midline structures.

ARP3beta, the gene encoding a new human actin-related protein, is alternatively spliced and predominantly expressed in brain neuronal cells.

A cDNA encoding a new human actin-related protein (ARP) was cloned. The corresponding protein is highly conserved with the previously described ARP3 protein, suggesting that it represents a second isoform of the human ARP3 subfamily. This new actin-related protein was subsequently named ARP3beta and represents the second example of multiple isoforms of an actin-related protein in a single organism. The ARP3beta gene was mapped to chromosome band 7q34, centromeric to Sonic Hedgehog. Gene structure analysis revealed that at least part of the observed ARP3beta mRNA heterogeneity is caused by alternative splicing resulting in exon skipping. Transcripts produced after exon 2 skipping are predicted to encode truncated products, whose functionality is still unclear. An ARP3beta pseudogene was detected on chromosome 2p11 by database searching. Several ARP3beta mRNA species were detected by Northern blotting and their abundance varied importantly among tissues: the highest expression levels were detected in fetal and adult brain, whereas lower levels were observed in liver, muscle and pancreas. In contrast, ARP3 mRNAs were detected in all tissues tested. Using in situ hybridization, the expression of ARP3beta in brain was shown to be restricted to neurons and epithelial cells from choroid plexus. This suggests a specific function for ARP3beta in the physiology of the development and/or maintenance of distinct subsets of nerve cells.

The molecular genetics of holoprosencephaly: a model of brain development for the next century.

The recent identification of some of the human holoprosencephaly genes is beginning to elucidate the intricate developmental programs that pattern normal and abnormal brain development. Here we present some of these advances in the context of our present understanding and conclude with some speculations regarding the direction for future investigations. We are living in a tremendously exciting time in medicine with the rapid application of molecular genetic approaches to the understanding of human disease. It is the purpose of this review to stress the underlying principals of our approach at a level that can be readily appreciated by colleagues who themselves are experts in brain anatomy but not necessarily the molecular genetics of brain development.