Ergativity in the Caucasus

This chapter provides an overview of ergativity-related phenomena in the languages of the Caucasus, a geographical region with a high concentration of ergative languages. The chapter reviews the morphologically ergative nature of the languages, revealed in case marking and gender agreement in Nakh-Daghestanian as well as person marking in Northwest Caucasian. No manifestation of syntactic ergativity is observed in languages of the Caucasus, with the exception of relativization in Circassian. It also reviews ergative splits observed in the Caucasus and describes attested patterns of split subject case marking in intransitive clauses. Finally, various properties usually thought to attest to the inherent or structural nature of ergative arguments are discussed: theta-relatedness, behavior in subject-to-subject raising, ability to participate in hierarchical agreement, the DP versus PP distinction, the structural locus of ergative case assignment, and some problems for configurational approaches to case assignment.

Aldehyde dehydrogenase is essential for both adult and larval ethanol resistance in Drosophila melanogaster

The enzyme aldehyde dehydrogenase (ALDH) is essential for ethanol metabolism in mammals, converting the highly toxic intermediate acetaldehyde to acetate. The role of ALDH in Drosophila has been debated, with some authors arguing that, at least in larvae, acetaldehyde detoxification is carried out mainly by alcohol dehydrogenase (ADH), the enzyme responsible for converting ethanol to acetaldehyde. Here, we report the creation and characterization of four null mutants of Aldh, the putative structural locus for ALDH. Aldh null larvae and adults are poisoned by ethanol concentrations easily tolerated by wild-types; their ethanol sensitivity is in fact comparable to that of Adh nulls. The results refute the view that ALDH plays only a minor role in ethanol detoxification in larvae, and suggest that Aldh and Adh may be equally important players in the evolution of ethanol resistance in fruit-breeding Drosophila.

Glutathione reductase activity deficiency in homozygous Gr1a1Neu mice does not cause haemolytic anaemia

A glutathione reductase (GR) mutant with approximately 50% residual enzyme activity in blood compared with wild-type was detected amongst offspring of isopropyl methanesulphonate-treated male mice. Homozygous mutants with only 2% residual enzyme activity were recovered in progeny of inter se matings of heterozygotes. Results of linkage studies indicate a mutation at the Gr1 structural locus on chromosome 8. The loss of GR activity was evident both in blood and in other tissue extracts. Erythrocyte and organo-somatic indices did not show differences between wild-types and homozygous mutants, indicating no association between the GR deficiency and haemolytic anaemia in this potential animal model.

A trans-acting regulatory gene that inversely affects the expression of the white, brown and scarlet loci in Drosophila.

A trans-acting regulatory gene, Inr-a, that alters the level of expression of the white eye color locus as an inverse function of the number of its functional copies is described. Several independent lines of evidence demonstrate that this regulatory gene interacts with white via the promoter sequences. Among these are the observations that the inverse regulatory effect is conferred to the Adh gene when fused to the white promoter and that cis-regulatory mutants of white fail to respond. The phenotypic response to Inr-a is found in all tissues in which white is expressed, and mutants of the regulator exhibit a recessive lethality during larval periods. Increased white messenger RNA levels in pupal stages are found in Inr-a/+ individuals versus +/+ and a coordinate response is observed for mRNA levels from the brown and scarlet loci. All are structurally related and participate in pigment deposition. These experiments demonstrate that a single regulatory gene can exert an inverse effect on a target structural locus, a situation postulated from segmental aneuploid studies of gene expression and dosage compensation.

A mutation resulting in increased triosephosphate isomerase activity in Mus musculus

SummaryA mutation resulting in increased triosephosphate isomerase (TPI) activity in blood was recovered in offspring of procarbazine hydrochloride-treated male mice. Breeding experiments indicated a codominant mode of expression. Compared to the wild type, heterozygous and homozygous mutants have mean erythrocyte TPI activities of approximately 140 and 190%, respectively. Besides blood and erythrocytes the increased activity is expressed to a similar degree in spleen, and to a lesser degree in liver, lung, kidney, muscle and brain. Enhanced activity was absent in the heart. Heterozygous and homozygous mutants are viable, fully fertile and exhibit no significant differences in haematological or other physiological traits studied. Biochemical investigations of TPI in both mutant genotypes revealed neither physicochemical nor kinetic differences compared to the wild type. Moreover, immunoinactivation studies showed no difference in the amount of antiplasma required to inactivate a constant amount of TPI activity in all three genotypes, strongly suggesting that the differences in enzyme activity are attributable to differing amounts of enzyme protein expressed per cell. Mapping studies indicated that the mutation is closely linked to the Gapd locus and consequently is located either adjacent to or within the Tpi-1 structural locus. It is hypothesized that the mutation affected a regulatory element contiguous to the Tpi-1 structural locus which acts by increasing the amount of TPI expressed.

Genetic analysis of the Shaker gene complex of Drosophila melanogaster.

The Shaker complex (ShC) spans over 350 kb in the 16F region of the X chromosome. It can be dissected by means of aneuploids into three main sections: the maternal effect (ME), the viable (V) and the haplolethal (HL) regions. The mutational analysis of ShC shows a high density of antimorphic mutations among 12 lethal complementation groups in addition to 14 viable alleles. The complex is the structural locus of a family of potassium channels as well as a number of functions relevant to the biology of the nervous system. The constituents of ShC seem to be linked by functional relationships in view of the similarity of the phenotypes, antimorphic nature of their mutations and the behavior in transheterozygotes. We discuss the relationship between the genetic organization of ShC and the functional coupling of potassium currents with the other functions encoded in the complex.