Type IV ATPases are putative aminophospholipid translocases (APLTs), more commonly known as flippases. A pronounced induction of the flippase Atp8a1 was observed in post-mortem tissue homogenates from the hippocampus and temporal lobe of juvenile autistic subjects compared to age-matched controls. In order to simulate the human data, C57BL/6 mice were allowed to develop after intra-hippocampal injection of recombinant lentivirus expressing Atp8a1 at the early developmental stage of postnatal day 6 (P6). Transmission electron microscopy (TEM) analysis of the lentivirus-Atp8a1 treated (Atp8a1+) mice in adulthood revealed fewer and weaker excitatory synapses in the hippocampal CA1 region compared to mice injected with empty virus. Significant inhibition of the Schaffer collateral pathway was observed in the Atp8a1+ mice in paired-pulse recording (PPR) at 20-ms inter-stimulus interval. In the three-chambered sociability test, the Atp8a1+ mice displayed no preference for an encaged stranger mouse over a novel object, which is a characteristic autistic-like behavior. In sharp contrast, Atp8a1 (-/-) mice displayed a preference for a stranger mouse over the novel object, which is characteristic of neurotypical mouse behavior. However, similar to the Atp8a1+ mice, the Atp8a1 (-/-) mice harbored fewer and weaker excitatory synapses in CA1 compared to wild-type controls, and displayed inhibition at 20-ms inter-stimulus interval in PPR. These findings suggest that both elevated and diminished levels of Atp8a1 during early development are detrimental to brain connectivity, but only elevated Atp8a1 is associated with aberrant social behavior. Mice with augmented levels of Atp8a1 may therefore serve as a potential model in autism research.
Homozygous mutations in the gene CLN1 typically result in infantile-onset neuronal ceroid lipofuscinosis, a severe progressive neurological disorder with early death. The gene CLN1 encodes the enzyme palmitoyl protein thioesterase (PPT1), which is involved in lysosomal degradation of S-fatty acylated proteins. Cysteamine bitartrate (Cystagon) has been shown to reduce the storage material in PPT1 deficient cells. We report the results of a 7-year, open label, nonrandomized trial using Cystagon in four individuals with juvenile-onset NCL resulting from milder CLN1 mutations. The Cystagon doses were gradually increased with the goal of achieving 50 mg/kg bodyweight. The disease progression was monitored with parental questionnaires in four treated individuals and five untreated controls with the same CLN1 mutations. Mononuclear leukocytes from the treated individuals were examined for submicroscopic lysosomal storage inclusions. Cystagon treatment resulted in decreased storage material in peripheral leukocytes of the treated individuals. No severe side effects were noted. An allergic rash occurred in one of the individuals that required a dose reduction. The treatment did not result in overall attenuation of the disease progression.
Summary: Two new observations have been made on human chromatid/chromosome ultrastructure using both scanning and transmission electron microscopy (SEM, TEM). A bipartite, apparently half-chromatid-like structure was observed in whole human chromosomes studied with SEM and in longitudinally sectioned chromosomes analyzed with TEM. In addition, we also observed a zipperlike configuration as the parallel sister chromatids separated likely due to the supercoiled structure of the chromosome and chromatid. It is possible that either or both of these new observations resulted from our (improved) method of preparing the chromosomes for SEM and TEM.
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