Behavioral Implications of Knockout for the Dyslexia-Risk Gene Dcdc2 in Mice

Several genetic linkage and epidemiological studies have provided strong evidence that DCDC2 is a candidate gene for developmental dyslexia, a disorder that impairs a person’s reading ability despite adequate intelligence, education, and socio-economic status. Studies investigating embryonic intra-ventricular RNA interference (RNAi) of Dcdc2, a rat homolog of the DCDC2 gene in humans, indicate disruptions in neuronal migration in the rat cortex during development. Interestingly, these anatomical anomalies are consistent with post mortem histological analysis of human dyslexic patients. Other rodent models of cortical developmental disruption have shown impairment in rapid auditory processing and learning maze tasks in affected subjects. The current study investigates the rapid auditory processing abilities of mice heterozygous for Dcdc2 (one functioning Dcdc2 allele) and mice with a homozygous knockout of Dcdc2 (no functioning Dcdc2 allele). It is important to note that this genetic model for behavioral assessment is still in the pilot stage. However, preliminary results suggest that mice with a genetic mutation of Dcdc2 have impaired rapid auditory processing, as well as non-spatial maze learning and memory ability, as compared to wildtypes. By genetically knocking out Dcdc2 in mice, behavioral features associated with Dcdc2 can be characterized, along with other neurological abnormalities that may arise due to the loss of the functioning gene.

Enhanced Cold Tolerance in Transgenic Tobacco Expressing a Chloroplast Omega-3 Fatty Acid Desaturase Gene under the Control of a Cold-inducible Promoter

A new cold-inducible genetic construct was cloned using a chloroplast-specific omega-3-fatty acid desaturase gene (FAD7) under the control of a cold-inducible promoter (cor15a) from Arabidopsis thaliana. RT-PCR confirmed a marked increase in FAD7 expression, in young Nicotiana tabacum (cv. Havana) plants harboring cor15a-FAD7, after a short-term exposure to cold. When young, cold-induced tobacco seedlings were exposed to low-temperature (0.5, 2 or 3.5 degrees C) for up to 44 days, survival within independent cor15a-FAD7 transgenic lines (40.2-96%) was far superior to the wild type (6.7-10.2%). In addition, the major trienoic fatty acid species remained stable in cold-induced cor15a-FAD7 N. tabacum plants under prolonged cold storage while the levels of hexadecatrienoic acid (16:3) and octadecatrienoic acid (18:3) declined in wild type plants under the same conditions (79 and 20.7% respectively). Electron microscopy showed that chloroplast membrane ultrastructure in cor15a-FAD7 transgenic plants was unaffected by prolonged exposure to cold temperatures. In contrast, wild type plants experienced a loss of granal stacking and disorganization of the thylakoid membrane under the same conditions. Changes in membrane integrity coincided with a precipitous decline in leaf chlorophyll concentration and low survival rates in wild type plants. Cold-induced double transgenic N. alata (cv. Domino Mix) plants, harboring both the cor15a-FAD7 cold-tolerance gene and a cor15a-IPT dark-tolerance gene, exhibited dramatically higher survival rates (89-90%) than wild type plants (2%) under prolonged cold storage under dark conditions (2 degrees C for 50 days).