Lc Mutation Research Articles

Electrical resistivity imaging inversion: An ISFLA trained kernel principal component wavelet neural network approach

The traditional artificial neural network (ANN) inversion of electrical resistivity imaging (ERI) based on gradient descent algorithm is known to be inept for its low computation efficiency and does not ensure global convergence. In order to solve above problems, a kernel principal component wavelet neural network (KPCWNN) trained by an improved shuffled frog leaping algorithm (ISFLA) method is proposed in this study. An additional kernel principal component (KPC) layer is applied to reduce the dimensionality of apparent resistivity data and increase the computational efficiency of wavelet neural network (WNN). Meanwhile, a novel ISFLA algorithm is adopted for improving the learning ability and inversion quality of WNN. In the proposed ISFLA, a hybrid LC mutation attractor is used to enhance the exploitation ability and a differential updating rule is used to enhance the exploration ability. Four groups of experiments are considered to demonstrate the feasibility of the proposed inversion method. The inversion results of the synthetic and field examples show that the introduced method is superior to other algorithms in terms of prediction accuracy and computational efficiency, which contribute to better inversion results.

Tomato Transcription Factor SlWUS Plays an Important Role in Tomato Flower and Locule Development.

Tomato is a model species for fleshy fruit development. The shapes and sizes of tomato (Solanum lycopersicum L.) are mainly controlled by several loci, including locule number (lc). Two single nucleotide polymorphisms were found downstream of WUSCHEL (SlWUS) in a putative tomato CArG cis-regulatory element. The lc mutation may affect the binding of AGAMOUS(AG), cause the up-regulation of SlWUS and result in increased locule numbers. In this study, tissue expression levels showed that SlWUS is expressed in young floral buds and shoot apexes. Silencing SlWUS on an lc mutant genetic background with an RNA interference (RNAi) strategy resulted in smaller flowers and fruit than those of the wild-type plants, with decreased locule number. Further study revealed that the SlWUS RNAi lines exhibited altered expression levels of the TAG1 and SlCLV3 genes that participate in the regulation of tomato flower and fruit locule development. In conclusion, this study provides the first genetic evidence that SlWUS may be the candidate gene of the lc locus and reveals the function of SlWUS in flower development.

Development of Hsp25 expression compartments is not constrained by Purkinje cell defects in the Lurcher mouse mutant

Four transverse zones can be distinguished in the adult mouse cerebellar cortex based on differential expression of cell-specific antigens, termination patterns of mossy fiber afferents, and phenotypes of mouse mutants with cerebellar defects: the anterior zone (AZ), central zone (CZ), posterior zone (PZ), and nodular zone (NZ). In the heterozygous Lurcher (Lc/+) mouse a zonally restricted abnormality in Purkinje cell development is seen. The Purkinje cell-specific antigen zebrin II is normally differentially expressed in all four zones of the adult cerebellum, but in the Lc/+ mutant is confined to the PZ and NZ, caudal to a transverse boundary in the dorsal aspect of lobule VIII. In this study we wanted to understand why zebrin II expression is arrested at this boundary and whether the Lc mutation affects the differentiation of additional Purkinje cell antigens in a similar manner. To determine this, we took advantage of the dynamic developmental timetable of another Purkinje cell antigen, the small heat shock protein Hsp25. Using immunohistochemistry we demonstrate that cerebellar maturation anterior to the CZ/PZ transverse boundary appears to be unaffected by the Lc allele, in that initial progression of Hsp25 expression in the Lc/+ cerebellum was similar to controls. Double-labeling experiments with anti-Hsp25 and anti-calbindin suggest that characteristic banding patterns of Hsp25 in Lc/+ cerebellum develop and are preserved despite cell loss. Thus, since simple temporal or spatial models cannot account for the zonal restriction seen during Lc/+ cerebellar development, the abnormality may be zebrin II-specific.

Motor coordination in mice with hotfoot, Lurcher, and double mutations of the Grid2 gene encoding the delta-2 excitatory amino acid receptor

Grid2 ho/ho is a loss of function gene mutation resulting in abnormal dendritic arborizations of Purkinje cells. These mutants were compared in a series of motor coordination tests requiring balance and equilibrium to nonataxic controls ( Grid2 ho/+ ) and to a double mutant ( Grid2 ho/Lc ) with an inserted Lc mutation. The performance of Grid2 ho/ho mutant mice was poorer than that of controls on stationary beam, coat hanger, unsteady platform, and rotorod tests. Grid2 ho/Lc did not differ from Grid2 Lc/+ mice. However, the insertion of the Lc mutation in Grid2 ho/Lc potentiated the deficits found in Grid2 ho/ho in stationary beam, unsteady platform, and rotorod tests. These results indicate a deleterious effect of the Lc mutation on Grid2-deficient mice.

Dominance of the lurcher mutation in heteromeric kainate and AMPA receptor channels.

Homomeric glutamate receptor (GluR) channels become spontaneously active when the last alanine residue within the invariant SYTANLAAF-motif in the third membrane segment is substituted by threonine. The same mutation in the orphan GluRdelta2 channel is responsible for neurodegeneration in "Lurcher" (Lc) mice. Since most native GluRs are composed of different subunits, we investigated the effect of an Lc-mutated subunit in heteromeric kainate and AMPA receptors expressed in HEK293 cells. Kainate receptor KA2 subunits, either wild type or carrying the Lc mutation (KA2(Lc)), are retained inside the cell but are surface-expressed when assembled with GluR6 subunits. Importantly, KA2(Lc) dominates the gating of KA2(Lc)/GluR6(WT) channels, as revealed by spontaneous activation and by slowed desensitization and deactivation kinetics of ligand-activated whole-cell currents. Moreover, the AMPA receptor subunit GluR-B(Lc)(Q) which forms spontaneously active homomeric channels with rectifying current-voltage relationships, dominates the gating of heteromeric GluR-B(Lc)(Q)/GluR-A(R) channels. The spontaneous currents of these heteromeric AMPAR channels show linear current-voltage relationships, and the ligand-activated whole-cell currents display slower deactivation and desensitization kinetics than the respective wild-type channels. For heteromeric Lc-mutated kainate and AMPA receptors, the effects on kinetics were reduced relative to the homomeric Lc-mutated forms. Thus, an Lc-mutated subunit can potentially influence heteromeric channel function in vivo, and the severity of the phenotype will critically depend on the levels of homomeric GluR(Lc) and heteromeric GluR(Lc)/GluR(WT) channels.

A new allele of the lurcher gene, lurcherJ.

A new neurological mouse mutation that arose spontaneously in a BALB/cByJ stock displays a semidominant pattern of inheritance. In the heterozygote, this mutation results in an early loss of Purkinje cells in the cerebellum, which is followed by the overt symptom of an ataxic gait first observed at postnatal day 13 (P13). A portion of animals homozygous for the mutation die within P0; the remaining homozygotes die by P25. The mutation maps to mouse Chromosome (Chr) 6 between markers D6Rck314 and D6Rck361, a chromosomal segment that contains the lurcher (Lc) locus. The Lc mutation is also semidominant and has a strikingly similar phenotype. A cross between a new mutant (Nm) heterozygote and an Lc heterozygote yields double heterozygotes, animals that carry both mutations, with a phenotype similar to that of both Nm and Lc homozygotes. The similarity in phenotype, the colocalization of the two loci on mouse Chr 6, and the positive result of the allelism test demonstrate that the new mutation is an allele of the Lc gene.

Generation of a high-resolution genetic map and a YAC contig of the Lurcher locus on mouse chromosome 6.

Lurcher (Lc) is a semidominant mouse mutant that displays progressive neurodegeneration during perinatal development. This genetic lesion results in apoptotic neuronal death in a dosage dependent and cell autonomous manner in specific neurons during their terminal differentiation. To understand the molecular basis of the Lc mutation, we have adopted a positional cloning approach based on its location on mouse chromosome 6. To define the Lc locus, we have extended our previous analysis of an intersubspecific backcross between Mus m. castaneus and B6CBACa-Aw-j/A-Lc consisting of 504 animals (Norman et al. 1991). In addition, 580 animals of a generic backcross between Mus spretus and C57BL/6 (The European Collaborative Interspecific Backcross) were utilized for the fine genetic mapping of the Lc locus. Using three RFLP markers and nine microsatellite markers in the vicinity of the Lc locus, we determined the order and relative genetic distances of these markers at a resolution of 0.1 cM. The Lc mutation was mapped between two flanking markers, D6Mit121 and D6Mit175, separated by a genetic distance of 0.5 cM. We then initiated the cloning of the genomic region surrounding these two markers by screening a YAC library and characterizing YAC end sequences for further screening. This effort has resulted in the construction of a YAC contig consisting of 14 YACs and spanning a 3-Mb region. Markers isolated from these YACs were used to further define the Lc locus, resulting in a physical map that places the Lc gene within an estimated 300-kb interval. This set of YACs and markers will serve as DNA sources for the identification of the Lc gene.

The lurcher gene induces apoptotic death in cerebellar Purkinje cells.

In the neurologically mutant mouse strain lurcher (Lc), heterozygous animals display cell autonomous degeneration of cerebellar Purkinje cells beginning in the second postnatal week. During the course of our studies to identify the genetic lesion responsible for this disease (Norman et al., 1991), we have formulated an hypothesis suggesting that in Lc Purkinje cells homeostasis is sufficiently perturbed to lead to the activation of programmed cell death, thus resulting in neuronal loss and the consequent neurologic disease (Heintz, 1993). To address this possibility, we have examined the properties of Lc Purkinje cells as they die during the second postnatal week. Our light and electron microscopic studies demonstrate that dying Lc Purkinje cells exhibit the characteristic morphologic features of apoptosis, including nuclear condensation, axon beading and membrane blebbing. Using an in situ end-labeling method, we have also detected nicked nuclear DNA in these cells. Furthermore, we have examined the expression of the sulfated glycoprotein 2 (SGP2), whose mRNA is induced in both T-cells and prostate epithelial cells undergoing apoptotic death. We show by in situ hybridization that SGP2 is not expressed at detectable levels in normal Purkinje cells, but that its mRNA is present in Lc Purkinje cells prior to their death. Also expression of the Kv3.3b potassium channel, which marks the terminal phase of Purkinje cell differentiation, is evident in Lc Purkinje cells prior to their death. These data demonstrate that the Lc mutation induces apoptosis in cerebellar Purkinje cells following their maturation in postnatal cerebellum. Isolation of the Lc mutation and further analysis of its action in eliciting apoptosis can provide an important opportunity for understanding the etiology of neurodegenerative disease.