Genetic mediation of infanticide and parental behavior in male and female domestic and wild stock house mice

Infanticide is a reproductive strategy found in many mammals, especially rodents. The proportion of male and female house mice (Mus domesticus) that are either infanticidal or noninfanticidal is strain specific and varies widely from stock to stock. Male house mice also show strain-specific variation in the behavioral mechanisms that inhibit infanticidal individuals from killing their own offspring. The adult offspring generated from reciprocally crossed CF-1 and Wild stock house mice were tested for their behavior toward newborn pups. In male CF-1xWild hybrids, the proportion of infanticidal and noninfanticidal males matched with their maternal phenotype, whereas female CF-1xWild hybrids exhibited a proportion of behaviors typical of the CF-1 phenotype, regardless of their mother's genotype. Our results suggest three conclusions: first, that infanticide is a highly labile and heritable behavior in both sexes; second, that there is a sex difference in the genetic substrate that regulates the inheritance of infanticidal behavior; and third, that selection pressures in male mice may operate independently on the mechanisms that promote spontaneous infanticidal behavior versus the mechanisms that inhibit infanticide.     

Translocation (X;20) involving the inactive X chromosome in a patient with myeloproliferative disorder

We report a patient with an unclassifiable myeloproliferative disorder and the rare t(X;20)(q13;q13.3) as the sole cytogenetic abnormality. The breakpoint on Xq is consistent with other reports of translocations involving the X chromosome with breakpoints that cluster to Xq13 and association with myeloid disorders. Late replication studies demonstrated the inactive X chromosome was involved in this translocation. The critical event in patients with myeloproliferative disease and deletion of 20q appears to be the loss of tumor suppressor genes. This may also be the mechanism in this patient with a potential cryptic deletion associated with the translocation. Alternatively, spreading of X inactivation into the derivative chromosome 20 provides a second mechanism for the loss of function of tumor suppressor genes on 20q. The finding in this patient of t(X;20) together with three others reported in the literature indicates that this may represent a primary non-random abnormality associated with myeloid malignancy, which may take on clinical significance with the accumulation of more cases.     

Bicuculline-induced circling from the rat superior colliculus is blocked by GABA microinjection into the deep cerebellar nuclei

In a recent electrophysiological experiment, we showed the deep cerebellar nuclei to be a major source of excitatory input to the superior colliculus. Furthermore, target neurons in the colliculus were found, in every case, to receive convergent tonic inhibitory input from the substantia nigra pars reticulata. In the present study, we investigated these effects in the awake rat. We asked whether circling behaviour, induced by unilateral injection of a GABA antagonist into the lateral colliculus, could be suppressed by concurrent cerebellar inactivation. Rats were chronically implanted with bilateral guide cannulae located above the superior colliculus and deep cerebellar nuclei. Bicuculline methiodide (25 pmol) was microinjected unilaterally into intermediate layers of the colliculus at increasing depths until an optimal contralateral circling response was elicited. This behaviour was taken as the baseline response and was the first of three treatments. The second was an identical manipulation of the colliculus with a concurrent 200-nl microinjection of 1 M GABA into the contralateral deep cerebellar nuclei. The third was a repeat of BIC alone into the colliculus or, if rotation had been suppressed by more than 50% on test 2, the treatment was collicular BIC plus deep cerebellar saline. This latter treatment was used as a control for possible non-pharmacological injection effects. The effect of cerebellar GABA at 26 sites (17 within cerebellar nuclei and 9 outside) on BIC-induced rotation at 15 collicular sites was studied in ten animals. Only GABA injections at sites that fell within the cerebellar nuclei significantly reduced turning (P<0.0001). A full behavioural analysis showed that this was a specific suppression of turning, not the result of general motor impairment. These results provide clear behavioural evidence that opposing, convergent influences from the basal ganglia and cerebellum interact in the lateral superior colliculus to control head and body movements. They furthermore suggest that the tonic deep cerebellar excitation of the superior colliculus could be the driving force in the expression of rotation induced by manipulations of the basal ganglia.     

Variable MHC class I engagement by Ly49 natural killer cell receptors demonstrated by the crystal structure of Ly49C bound to H-2K(b)

The Ly49 family of natural killer (NK) receptors regulates NK cell function by sensing major histocompatibility complex (MHC) class I. Ly49 receptors show complex patterns of MHC class I cross-reactivity and, in certain cases, peptide selectivity. To investigate whether specificity differences result from topological differences in MHC class I engagement, we determined the structure of the peptide-selective receptor Ly49C in complex with H-2K(b). The Ly49C homodimer binds two MHC class I molecules in symmetrical way, a mode distinct from that of Ly49A, which binds MHC class I asymmetrically. Ly49C does not directly contact the MHC-bound peptide. In addition, MHC crosslinking by Ly49C was demonstrated in solution. We propose a dynamic model for Ly49-MHC class I interactions involving conformational changes in the receptor, whereby variations in Ly49 dimerization mediate different MHC-binding modes.     

Noradrenergic and opioidergic alterations in neuropathy in different rat strains

The Fischer 344 (F344) rat strain differs from the Lewis strain in the response to neuropathic pain. Recently, we found that F344 rats totally recover from mechanical allodynia induced by chronic constriction injury (CCI) of the sciatic nerve 28 days after surgery whereas Lewis rats are initiating their recovery at this time point. Thus, the use of this neuropathic pain model in these different rat strains constitutes a good strategy to identify possible target genes involved in the development of neuropathic pain. Since differences between Lewis and F344 rats in their response to pain stimuli in acute pain models have been related to differences in the endogenous opioid and noradrenergic systems, we aimed to determine the levels of expression of key genes of both systems in the spinal cord and dorsal root ganglia (DRG) of both strains 28 days after CCI surgery. Real time RT-PCR revealed minimal changes in gene expression in the spinal cord after CCI despite the strain considered, but marked changes in DRG were observed. A significant upregulation of prodynorphin gene expression occurred only in injured DRG of F344 rats, the most resistant strain to neuropathic pain. In addition, we found a significant downregulation of tyrosine hydroxylase and proenkephalin gene expression levels in both strains whereas δ-opioid receptor was found to be significantly downregulated only in injured DRG of Lewis rats although the same trend was observed in F344 rats. The data strongly suggest that dynorphins could be involved in strain differences concerning CCI resistance.     

Development and evaluation of NucliSens basic kit NASBA for diagnosis of parainfluenza virus infection with 'end-point' and 'real-time' detection

New methods for the detection of human parainfluenza viruses (HPIVs) were developed. These were based on nucleic acid sequence-based amplification (NASBA) and utilised the NucliSens Basic Kit. Primers and probes were selected from the haemagglutinin neuraminidase (HN) gene of HPIV1, HPIV2 and HPIV3, and from the phosphoprotein (P) of HPIV4a and -4b. Synthetic RNA, titrated control virus stocks and respiratory specimens (n=44) were utilised to evaluate performance of the assays. Detection of NASBA products was by probe hybridisation and electrochemiluminescence (ECL) ('end-point' detection) or using molecular beacons ('real-time' detection). The assays using ECL detection proved to be both sensitive and specific. Typically, less than or equal to 100 RNA copies or one TCID(50) input was detectable with no cross-reaction between the specific HPIV assays and other respiratory viruses. Results for clinical samples were concordant with those obtained by 'conventional' procedures by classical viral diagnostic methods. 'Real-time' detection utilised probes specific for either HPIV1 or HPIV3 with similar performance characteristics to the assays with 'end-point' detection. The feasibility of multiplexing targets together was confirmed using a combined HPIV1 and HPIV3 assay with good results for ECL and molecular beacon detection on control material and clinical samples.     

Cigarette smoke prevents apoptosis through inhibition of caspase activation and induces necrosis

Emphysema is characterized by enlargement of the distal airspaces in the lungs due to destruction of alveolar walls. Alveolar endothelial and epithelial cell apoptosis induced by cigarette smoke is thought to be a possible mechanism for this cell loss. In contrast, our studies show that cigarette smoke condensate (CSC) induces necrosis in alveolar epithelial cells and human umbilical vein endothelial cells. Furthermore, study of the cell death pathway in a model system using Jurkat cells revealed that in addition to inducing necrosis, CSC inhibited apoptosis induced by staurosporine or Fas ligation, with both effects prevented by the antioxidants glutathione and dithiothreitol. Time course experiments revealed that CSC inhibited an early step in the caspase cascade, whereby caspase-3 was not activated. Moreover, cell-free reconstitution of the apoptosome in cytoplasmic extracts from CSC-treated cells, by addition of cytochrome-c and dATP, did not result in activation of caspases-3 or -9. Thus, smoke treatment may alter the levels of pro- and antiapoptogenic factors downstream of the mitochondria to inhibit active apoptosome formation. Therefore, unlike previous studies, cell death in response to cigarette smoke by necrosis and not apoptosis may be responsible for the loss of alveolar walls and inflammation observed in emphysema.     

Novel FARS2 variants in patients with early onset encephalopathy with or without epilepsy associated with long survival

Mitochondrial translation is essential for the biogenesis of the mitochondrial oxidative phosphorylation system (OXPHOS) that synthesizes the bulk of ATP for the cell. Hypomorphic and loss-of-function variants in either mitochondrial DNA or in nuclear genes that encode mitochondrial translation factors can result in impaired OXPHOS biogenesis and mitochondrial diseases with variable clinical presentations. Compound heterozygous or homozygous missense and frameshift variants in the FARS2 gene, that encodes the mitochondrial phenylalanyl-tRNA synthetase, are commonly linked to either early-onset epileptic mitochondrial encephalopathy or spastic paraplegia. Here, we expand the genetic spectrum of FARS2-linked disease with three patients carrying novel compound heterozygous variants in the FARS2 gene and presenting with spastic tetraparesis, axial hypotonia and myoclonic epilepsy in two cases.Subject terms: Metabolic disorders, Mutation