Related Experiment Videos
Neuroanatomical study of somatomotor cortex in microcephalic mice induced by cytosine arabinoside
Abstract:
Somatomotor cortex of mice with microcephaly induced by DNA polymerase inhibitor cytosine arabinoside (Ara-C), has been studied with a modified Golgi-Cox staining and a HRP retrograde tracing method. Microcephalic mice were prepared by prenatal injections of cytosine arabinoside on days 13.5 and 14.5 of pregnancy. Cytoarchitectonically, the cerebral cortices of adult microcephalic mice are characterized by atypical pyramidal cells with abnormal dendrites and irregular patterns of cellular lamination. Semiquantitative analyses of the abnormality of dendrites in Golgi-Cox preparation indicate that both the degree and direction of ramification are severely affected in Ara-C treated mice. In adult control cerebrum, original neurons of corticospinal tract labeled after HRP injection into the lumbar cord were situated in layer V. In the microcephalic brains, however, HRP labeled neurons, some of which had abnormal polarity, were scattered throughout all layers. This HRP study for corticospinal tract neurons also confirms the irregular pattern of the cortex in which only three layers are recognized.
Insights
Prenatal exposure to cytosine arabinoside (Ara-C) in mice causes microcephaly, leading to abnormal brain development. This includes altered pyramidal cells, dendritic defects, and disorganized cortical layers affecting corticospinal tract neurons.
Area of Science:
- Neuroscience
- Developmental Biology
- Toxicology
Background:
- Microcephaly is a condition characterized by an abnormally small head and brain.
- Cytosine arabinoside (Ara-C) is a DNA polymerase inhibitor with teratogenic potential.
Purpose of the Study:
- To investigate the structural and cytoarchitectural changes in the somatomotor cortex of mice with Ara-C induced microcephaly.
- To analyze the impact of Ara-C on pyramidal cell morphology and corticospinal tract neuron organization.
Main Methods:
- Induction of microcephaly in mice via prenatal injection of cytosine arabinoside (Ara-C) on gestational days 13.5 and 14.5.
- Modified Golgi-Cox staining for detailed neuronal morphology and dendritic analysis.
- Horseradish peroxidase (HRP) retrograde tracing to identify and characterize corticospinal tract neurons.
Main Results:
- Microcephalic mice exhibited atypical pyramidal cells with abnormal dendrites and irregular cortical lamination.
- Quantitative analysis revealed severe defects in dendritic ramification (degree and direction) in Ara-C treated mice.
- HRP tracing showed corticospinal tract neurons, normally in layer V, were scattered across all cortical layers in microcephalic brains, with some displaying abnormal polarity. Only three cortical layers were discernible.
Conclusions:
- Prenatal exposure to Ara-C induces significant cytoarchitectural abnormalities in the developing mouse brain, impacting neuronal morphology and organization.
- These structural disruptions, particularly in the somatomotor cortex and corticospinal tract, underlie the observed microcephaly.
- The study highlights the critical role of proper cortical lamination and neuronal development during sensitive prenatal periods.