Bilateral subcortical heterotopia with partial callosal agenesis in a mouse mutant.

Cognition and behavior depend on the precise placement and interconnection of complex ensembles of neurons in cerebral cortex. Mutations that disrupt migration of immature neurons from the ventricular zone to the cortical plate have provided major insight into mechanisms of brain development and disease. We have discovered a new and highly penetrant spontaneous mutation that leads to large nodular bilateral subcortical heterotopias with partial callosal agenesis. The mutant phenotype was first detected in a colony of fully inbred BXD29 mice already known to harbor a mutation in Tlr4. Neurons confined to the heterotopias are mainly born in midgestation to late gestation and would normally have migrated into layers 2-4 of overlying neocortex. Callosal cross-sectional area and fiber number are reduced up to 50% compared with coisogenic wildtype BXD29 substrain controls. Mutants have a pronounced and highly selective defect in rapid auditory processing. The segregation pattern of the mutant phenotype is most consistent with a two-locus autosomal recessive model, and selective genotyping definitively rules out the Tlr4 mutation as a cause. The discovery of a novel mutation with strong pleiotropic anatomical and behavioral effects provides an important new resource for dissecting molecular mechanisms and functional consequences of errors of neuronal migration.

Potential role of Atp5g3 in epigenetic regulation of alcohol preference or obesity from a mouse genomic perspective.

The mitochondrial ATP synthase, subunit c, isoform 3 gene (Atp5g3) encodes subunit 9, the subunit of the multisubunit enzyme that catalyzes ATP synthesis during oxidative phosphorylation in mitochondria. According to the Ensembl database, Atp5g3 in mice is located on chromosome 2 between 73746504 and 73749383 bp, within the genomic regions of two sets of quantitative trait loci - alcohol preference and body weight. Both of those traits are more influenced by epigenetic factors than many other traits are. Using currently available phenotype and gene expression profiles from the GeneNetwork database, we obtained correlations between Atp5g3 and alcoholism- and obesity-relevant phenotypes. The correlation in expression levels between Atp5g3 and each of its 12 partner genes in the molecular interaction are different in various tissues and genes. Transcriptome mapping indicated that Atp5g3 is differentially regulated in the hippocampus, cerebellum, and liver. Owing to a lack of known polymorphisms of Atp5g3 among three relevant mouse strains, C57BL/6J (B6), DBA/2J (D2), and BALB/ cJ, the molecular mechanism for the connection between Atp5g3 and alcoholism and body weight requires further investigation.

Polyglucosan body density in the aged mouse hippocampus is controlled by a novel modifier locus on chromosome 1.

Aging can be associated with the accumulation of hypobranched glycogen molecules (polyglucosan bodies, PGBs), particularly in astrocytes of the hippocampus. While PGBs have a detrimental effect on cognition in diseases such as adult polyglucosan body disease and Lafora disease, the underlying mechanism and clinical relevance of age-related PGB accumulation remains unknown. Here, we have investigated the genetic basis and functional impact of age-related PGB accumulation in 32 fully sequenced BXD-type strains of mice which exhibit a 400-fold variation in PGB burden in 16-18 month old females. We mapped a major locus controlling PGB density in the hippocampus to chromosome 1 at 72-75 Mb (linkage of 4.9 -logP), which we defined as the Pgb1 locus. To identify potentially causal gene variants within Pgb1, we generated extensive hippocampal transcriptome datasets and identified two strong candidate genes for which mRNA correlates with PGB density-Smarcal1 and Usp37. In addition, both Smarcal1 and Usp37 contain non-synonymous allele variations likely to impact protein function. A phenome-wide association analysis highlighted a trans-regulatory effect of the Pgb1 locus on expression of Hp1bp3, a gene known to play a role in age-related changes in learning and memory. To investigate the potential impact of PGBs on cognition, we performed conditioned fear memory testing on strains displaying varying degrees of PGB burden, and a phenome-wide association scan of ~12,000 traits. Importantly, we did not find any evidence suggesting a negative impact of PGB burden on cognitive capacity. Taken together, we have identified a major modifier locus controlling PGB burden in the hippocampus and shed light on the genetic architecture and clinical relevance of this strikingly heterogeneous hippocampal phenotype.

Neonatal immunisation against a novel gonadotrophin-releasing hormone construct delays the onset of gonadal growth and puberty in bull calves.

The aim of the present study was to investigate the effect of the neonatal immunisation of bull calves against a novel gonadotrophin-releasing hormone (GnRH) construct, comprised of GnRH coupled to the glycoprotein D subunit of the bovine herpes virus-1 (GnRH-BHV1 gD), on endocrine status, reproductive organ development and carcass quality. Eighteen bull calves received either GnRH construct (n=9) or saline (control; n=9) at 2, 6 and 13.5 weeks of age. Blood samples were taken to determine antibody titres against GnRH, FSH and testosterone (T) concentrations and LH pulse characteristics, with testicular circumference monitored monthly. Immunisation reduced LH pulse amplitude (P<0.05) and T concentrations (P<0.05), particularly at the peak in anti-GnRH titres after the second booster at 16 weeks of age (P<0.001), but not when titres fell. Despite antibody titres decreasing after 16 weeks, immunisation reduced testicular size between 16 to 57 weeks of age (P<0.05), provoking an 8-week delay in puberty onset, defined as testicular circumference ≥14 cm. In conclusion, neonatal immunisation induced a significant immune response against GnRH, provoking a temporary endocrine disturbance that had a long-term effect on testicular development, delaying the onset of puberty. These results support the hypothesis that a developmental window exists during testicular development, such that disturbance of the endocrine drive to the gonads during this period results in a longer-term impairment of gonadal function.

Immunoglobulin heavy chain variable region genes contribute to the induction of thyroid-stimulating antibodies in recombinant inbred mice.

Graves' hyperthyroidism is an autoimmune disease occurring spontaneously in humans and caused by autoantibodies that stimulate the thyrotropin receptor. In mice, inducing Graves'-like hyperthyroidism requires in vivo expression of the thyrotropin receptor using plasmid or adenovirus vectors. However, mice with different genetic backgrounds vary markedly in their susceptibility to induced hyperthyroidism. Further, in some strains major disparities exist between the induction of hyperthyroidism and detection of thyroid-stimulating antibodies. To break tolerance, virtually all Graves' mouse models involve immunization with human thyrotropin-receptor DNA and the standard thyroid-stimulating antibody bioassay uses cells expressing the human thyrotropin receptor. We hypothesized, and now report, that disparities between hyperthyroidism and thyroid-stimulating antibody bioactivity are explained, at least in part, by differential antibody recognition of the human vs the mouse thyrotropin receptor. The genetic basis for these species differences was explored using genotyped, recombinant-inbred mouse strains. We report that loci in the immunoglobulin heavy chain variable region as well as in the major histocompatibility complex region contribute in a strain-specific manner to the development of antibodies specific for the human or the mouse thyrotropin receptor. The novel finding of a role for immunoglobulin heavy chain variable region gene involvement in thyroid-stimulating antibody epitopic specificity provides potential insight into genetic susceptibility in human Graves' disease.

Antisense transcription: a critical look in both directions.

The mammalian genome contains a large layer of hidden biological information. High-throughput methods have provided new insights into the regulatory networks that orchestrate the "when, where and how" of gene expression, revealing a complex interplay between proteins, regulatory RNAs, and chemical and structural alterations of the genome itself. Naturally occurring antisense transcription has been considered as an important feature in creating transcriptional and hence cellular and organismal complexity. Here, we review the current understanding of the extent, functions and significance of antisense transcription. We critically discuss results from genome-wide studies and documented examples of individual antisense transcripts. So far, the regulatory potential of gene overlaps has been demonstrated only in a few selected cases of experimentally characterized antisense transcripts. Facing the large-scale antisense transcription observed in eukaryotic genomes, it still remains an open challenge to distinguish transcriptional noise from biological function of gene overlapping patterns.

Genetic dissection of the mouse brain using high-field magnetic resonance microscopy.

Magnetic resonance (MR) imaging has demonstrated that variation in brain structure is associated with differences in behavior and disease state. However, it has rarely been practical to prospectively test causal models that link anatomical and functional differences in humans. In the present study we have combined classical mouse genetics with high-field MR to systematically explore and test such structure-functional relations across multiple brain regions. We segmented 33 regions in two parental strains-C57BL/6J (B) and DBA/2J (D)-and in nine BXD recombinant inbred strains. All strains have been studied extensively for more than 20 years using a battery of genetic, functional, anatomical, and behavioral assays. We compared levels of variation within and between strains and sexes, by region, and by system. Average within-strain variation had a coefficient of variation (CV) of 1.6% for the whole brain; while the CV ranged from 2.3 to 3.6% for olfactory bulbs, cortex and cerebellum, and up to approximately 18% for septum and laterodorsal thalamic nucleus. Variation among strain averages ranged from 6.7% for cerebellum, 7.6% for whole brain, 9.0% for cortex, up to approximately 26% for the ventricles, laterodorsal thalamic nucleus, and the interpeduncular nucleus. Heritabilities averaged 0.60+/-0.18. Sex differences were not significant with the possible (and unexpected) exception of the pons ( approximately 20% larger in males). A correlation matrix of regional volumes revealed high correlations among functionally related parts of the CNS (e.g., components of the limbic system), and several high correlations between regions that are not anatomically connected, but that may nonetheless be functionally or genetically coupled.

Formation of retinal ganglion cell topography during prenatal development.

A fundamental feature of the mammalian visual system is the nonuniform distribution of ganglion cells across the retinal surface. To understand the ontogenetic processes leading to the formation of retinal ganglion cell topography, changes in the regional density of these neurons were studied in relation to ganglion cell loss and the pattern of retinal growth in the fetal cat. Midway through the gestation period, the density of these neurons was only two to three times greater in the area centralis than in the peripheral retina, whereas shortly before birth this central-to-peripheral difference was nearly 20-fold. Age-related changes in the ganglion cell distribution were found not to correspond in time or magnitude to the massive loss of ganglion cells that occurs during prenatal development. Rather, the formation of ganglion cell density gradients can be accounted for by unequal expansion of the growing fetal retina-peripheral regions expand more than the central region, thereby diluting the peripheral density of ganglion cells to a greater degree. Nonuniform growth, in conjunction with differential periods of neurogenesis of the different types of retinal cells, appears to be a dominant factor regulating overall retinal topography. These results suggest that the differential regional expansion of the fetal retina underlies the formation of magnification factors in the developing visual system.

Prion domain initiation of amyloid formation in vitro from native Ure2p.

The [URE3] non-Mendelian genetic element of Saccharomyces cerevisiae is an infectious protein (prion) form of Ure2p, a regulator of nitrogen catabolism. Here, synthetic Ure2p1-65 were shown to polymerize to form filaments 40 to 45 angstroms in diameter with more than 60 percent beta sheet. Ure2p1-65 specifically induced full-length native Ure2p to copolymerize under conditions where native Ure2p alone did not polymerize. Like Ure2p in extracts of [URE3] strains, these 180- to 220-angstrom-diameter filaments were protease resistant. The Ure2p1-65-Ure2p cofilaments could seed polymerization of native Ure2p to form thicker, less regular filaments. All filaments stained with Congo Red to produce the green birefringence typical of amyloid. This self-propagating amyloid formation can explain the properties of [URE3].

Post-genomic behavioral genetics: From revolution to routine.

What was once expensive and revolutionary-full-genome sequence-is now affordable and routine. Costs will continue to drop, opening up new frontiers in behavioral genetics. This shift in costs from the genome to the phenome is most notable in large clinical studies of behavior and associated diseases in cohorts that exceed hundreds of thousands of subjects. Examples include the Women's Health Initiative (www.whi.org), the Million Veterans Program (www. RESEARCH: va.gov/MVP), the 100 000 Genomes Project (genomicsengland.co.uk) and commercial efforts such as those by deCode (www.decode.com) and 23andme (www.23andme.com). The same transition is happening in experimental neuro- and behavioral genetics, and sample sizes of many hundreds of cases are becoming routine (www.genenetwork.org, www.mousephenotyping.org). There are two major consequences of this new affordability of massive omics datasets: (1) it is now far more practical to explore genetic modulation of behavioral differences and the key role of gene-by-environment interactions. Researchers are already doing the hard part-the quantitative analysis of behavior. Adding the omics component can provide powerful links to molecules, cells, circuits and even better treatment. (2) There is an acute need to highlight and train behavioral scientists in how best to exploit new omics approaches. This review addresses this second issue and highlights several new trends and opportunities that will be of interest to experts in animal and human behaviors.

A quantitative trait locus on chromosome 1 modulates intermale aggression in mice.

Aggression between male conspecifics is a complex social behavior that is likely modulated by multiple gene variants. In this study, the BXD recombinant inbred mouse strains (RIS) were used to map quantitative trait loci (QTLs) underlying behaviors associated with intermale aggression. Four hundred and fifty-seven males from 55 strains (including the parentals) were observed at an age of 13 ± 1 week in a resident-intruder test following 10 days of isolation. Attack latency was measured directly within a 10-minute time period and the test was repeated 24 hours later. The variables we analyzed were the proportion of attacking males in a given strain as well as the attack latency (on days 1 and 2, and both days combined). On day 1, 29% of males attacked, and this increased to 37% on day 2. Large strain differences were obtained for all measures of aggression, indicating substantial heritability (intraclass correlations 0.10-0.18). We identified a significant QTL on chromosome (Chr) 1 and suggestive QTLs on mouse Chrs 1 and 12 for both attack and latency variables. The significant Chr 1 locus maps to a gene-sparse region between 82 and 88.5 Mb with the C57BL/6J allele increasing aggression and explaining about 18% of the variance. The most likely candidate gene modulating this trait is Htr2b which encodes the serotonin 2B receptor and has been implicated in aggressive and impulsive behavior in mice, humans and other species.

Contemporary surgical management of hypodontia.

Hypodontia is the term most commonly applied to the condition in which teeth congenitally fail to develop. Such cases differ from teeth that have been lost early or that have failed to erupt, although their initial presentation may be similar and therefore not recognised. The range of missing teeth and their physical and psychological results is large, and the difference in complexity in the management of a patient with isolated hypodontia compared with one with oligodontia or anodontia together with skeletal and orthognathic discrepancies should not be underestimated. Surgical interventions primarily involve augmentation of bone before placement of an implant, but may include techniques such as distraction osteogenesis and orthognathic surgery. These patients are best managed by a multidisciplinary team, and in this review our aim has been to describe the role of oral and maxillofacial surgeons within it.

Success rates and complications of autologous onlay bone grafts and sinus lifts in patients with congenital hypodontia and after trauma.

Autogenous bone remains the gold standard for augmentation of the alveolar ridge in congenital hypodontia and appreciable post-traumatic deformity. This generally reflects the volume of material required for such defects and the osteogenic potential of the grafts. Morbidity at the donor site and success rates may lead to autogenous grafts being superseded by xenografts or alloplastic materials in the future, but we know of little evidence to confirm this. All patients having augmentation of the alveolar ridge or sinus lift to enable subsequent placement of implants between 01 January 2009 and 31 December 2016 were identified from a prospectively-gathered database held at the Queen Elizabeth Hospital, Birmingham. Morbidity was recorded, with overall success defined as a graft that enabled subsequent placement of an implant. During this period the following grafts: calvarial (n=4), iliac crest (n=4), and ramus (n=149) were recorded, as well as 53 sinus lifts. Sinus lift augmentation with BioOss® had the highest success rate (51/53). Calvarial and iliac crest grafts had higher failure rates (2/4 and 3/4, respectively) than those from the mandibular ramus (6/149, 4%). Fifteen of 149 (10%) ramus grafts resulted in transient anaesthesia of the inferior alveolar nerve but no patients developed any permanent morbidity at the donor or recipient sites. Ramus grafts are a predictable method of bone augmentation with only transient morbidity at the donor site. Higher failure rates for extraoral grafts probably reflect their use in more challenging cases when more bone is required. Bilateral ramus grafts are an alternative to extraoral grafts and may be supplemented by bovine-derived particulate grafts with no appreciable increase in complications.

QTL and systems genetics analysis of mouse grooming and behavioral responses to novelty in an open field.

The open field is a classic test used to assess exploratory behavior, anxiety and locomotor activity in rodents. Here, we mapped quantitative trait loci (QTLs) underlying behaviors displayed in an open field, using a panel of 53 BXD recombinant inbred mouse strains with deep replication (10 per strain and sex). The use of these strains permits the integration and comparison of data obtained in different laboratories, and also offers the possibility to study trait covariance by exploiting powerful bioinformatics tools and resources. We quantified behavioral traits during 20-min test sessions including (1) percent time spent and distance traveled near the wall (thigmotaxis), (2) leaning against the wall, (3) rearing, (4) jumping, (5) grooming duration, (6) grooming frequency, (7) locomotion and (8) defecation. All traits exhibit moderate heritability making them amenable to genetic analysis. We identified a significant QTL on chromosome M.m. 4 at approximately 104 Mb that modulates grooming duration in both males and females (likelihood ratio statistic values of approximately 18, explaining 25% and 14% of the variance, respectively) and a suggestive QTL modulating locomotion that maps to the same locus. Bioinformatic analysis indicates Disabled 1 (Dab1, a key protein in the reelin signaling pathway) as a particularly strong candidate gene modulating these behaviors. We also found 2 highly suggestive QTLs for a sex by strain interaction for grooming duration on chromosomes 13 and 17. In addition, we identified a pairwise epistatic interaction between loci on chromosomes 12 at 36-37 Mb and 14 at 34-36 Mb that influences rearing frequency in males.

Lineage versus environment in embryonic retina: a revisionist perspective.

The idea that microenvironmental cues act alone late in development to determine a cell's phenotype has dominated recent discussion of, retinal development, and has successfully displaced the notion of any role for cell lineage in the process of cell determination. We argue that there is, in fact, evidence favoring a degree of lineage restriction during the development of the vertebrate retina. We propose that environmental factors modulate a process of progressive lineage restriction. In this model, progenitor cells are viewed as having unequal potential, and their progeny are viewed as being committed to one of the major retinal cell classes before the stage at which they become postmitotic.

Fast-track referrals for oral lesions: a prospective study.

Since the introduction of the 14-day rule for referrals for cancer in 1999 there has been some suspicion that rates of detection of cancer are low and the number of inappropriate referrals is high. We undertook a prospective study of 150 consecutive patients with oral lesions referred to a department of oral and maxillofacial surgery in a teaching hospital that uses a "two week wait" fast-track referral system for head and neck cancers. The main outcome measures were the number of cancers detected, the age and sex of the patients, the number seen within 2 weeks, by whom, and the final diagnosis. Most patients (n=120, 80%) were referred with oral ulceration. All patients were seen within 2 weeks (mean 6 days). Nine patients (6%) had a diagnosis of malignancy and 17 (11%) had no detectable abnormality. The study confirms what others have shown, that the yield of diagnoses of malignant disease from fast-track referrals is low and the number of non-urgent referrals is high.

Genetic control of the mouse cerebellum: identification of quantitative trait loci modulating size and architecture.

To discover genes influencing cerebellum development, we conducted a complex trait analysis of variation in the size of the adult mouse cerebellum. We analyzed two sets of recombinant inbred BXD strains and an F2 intercross of the common inbred strains, C57BL/6J and DBA/2J. We measured cerebellar size as the weight or volume of fixed or histologically processed tissue. Among BXD recombinant inbred strains, the cerebellum averages 52 mg (12.4% of the brain) and ranges 18 mg in size. In F2 mice, the cerebellum averages 62 mg (12.9% of the brain) and ranges approximately 20 mg in size. Five quantitative trait loci (QTLs) that significantly control variation in cerebellar size were mapped to chromosomes 1 (Cbs1a), 8 (Cbs8a), 14 (Cbs14a), and 19 (Cbs19a, Cbs19b). In combination, these QTLs can shift cerebellar size an appreciable 35% of the observed range. To assess regional genetic control of the cerebellum, we also measured the volume of the cell-rich, internal granule layer (IGL) in a set of BXD strains. The IGL ranges from 34 to 43% of total cerebellar volume. The QTL Cbs8a is significantly linked to variation in IGL volume and is suggestively linked to variation in the number of cerebellar folia. The QTLs we have discovered are among the first loci shown to modulate the size and architecture of the adult mouse cerebellum.

Complex trait analysis of the hippocampus: mapping and biometric analysis of two novel gene loci with specific effects on hippocampal structure in mice.

Notable differences in hippocampal structure are associated with intriguing differences in development and behavioral capabilities. We explored genetic and environmental factors that modulate hippocampal size, structure, and cell number using sets of C57BL/6J (B6) and DBA/2J (D2) mice; their F1 and F2 intercrosses (n = 180); and 35 lines of BXD recombinant inbred (RI) strains. Hippocampal weights of the parental strains differ by 20%. Estimates of granule cell number also differ by approximately 20%. Hippocampal weights of RI strains range from 21 to 31 mg, and those of individual F2 mice range from 23 to 36 mg (bilateral weights). Volume and granule cell number are well correlated (r = 0.7-0.8). Significant variation is associated with differences in age and sex. The hippocampus increases in weight by 0.24 mg per month, and those of males are 0.55 mg heavier (bilateral) than those of females. Heritability of variation is approximately 50%, and half of this genetic variation is generated by two quantitative trait loci that map to chromosome 1 (Hipp1a: genome-wide p < 0.005, between 65 and 100 cM) and to chromosome 5 (Hipp5a, p < 0.05, between 15 and 40 cM). These are among the first gene loci known to produce normal variation in forebrain structure. Hipp1a and Hipp5a individually modulate hippocampal weight by 1.0-2.0 mg, an effect size greater than that generated by age or sex. The Hipp gene loci modulate neuron number in the dentate gyrus, collectively shifting the population up or down by as much as 200,000 cells. Candidate genes for the Hipp loci include Rxrg and Fgfr3.

Asymmetric connections, duplicate layers, and a vertically inverted map in the primary visual system.

The achiasmatic mutation is a remarkable and rare visual system mutation carried in a line of black sheepdogs. In affected animals, the optic chiasm is missing, and each retina projects entirely to the ipsilateral hemisphere. As a result of this navigational error, maps of visual space in the lateral geniculate nucleus (LGN) have a unique structure with mirror reversals of field position across the A-A1 border. Animals also have a persistent and severe congenital nystagmus. In this report we analyze a novel variant of the achiasmatic mutation, one in which retinal axons from only one eye successfully cross midline and in which the great majority of fibers from both eyes terminate in a single lateral geniculate nucleus. The dominant optic tract contains four times as many axons as the other tract. The hyperinnervated LGN has a lamination pattern consisting of duplicate and partly interwoven layers. A multiunit mapping study of visual cortex (primarily area 17 along the marginal gyrus) shows that receptive field topography and orientation selectivity are normal. The size of central binocular visual space is nearly normal and is flanked by monocular domains in the periphery. However, there is an inexplicable vertical inversion in the orientation of the cortical representation: superior fields are located rostrally, and inferior fields are located caudally. Despite a host of drastic abnormalities at all level of the visual system, from retina to cortex, this animal was behaviorally indistinguishable from normal dogs and did not have any detectable oculomotor abnormalities.

Laser Raman studies of lipid disordering by the B-protein of fd phage.

Complexes of the B-protein of fd phage with the model lipid dipalmitoyl phosphatidylcholine (DPPC) were made by sonication of the fd phage in the presence of dipalmitoyl phosphatidylcholine. Both laser Raman spectra and circular dichroism show the protein in the membrane to be almost entirely in the beta-sheet conformation. This beta-sheet conformation is found to be independent of the temperature between 10 degrees C and 50 degrees C. On the other hand, the protein has a very dramatic effect on the organization of the lipid bilayer. An aqueous dispersion of 1 : 1 lipid/protein mixture gives a broad conformational transition of DPPC which occurs between 10 degrees C and 30 degrees C. This contrasts markedly with simple aqueous DPPC dispersions which show a sharp transition at 41 degrees C. This appears to be the first reported example of the lowering of the conformational transition of a membrane bilayer by an intrinsic membrane protein.