Brain development in hydrocephalic-polydactyl, a recessive pleiotropic mutant in the mouse

Area of Science:

• Developmental biology
• Neuroscience
• Genetics

Background:

• The hydrocephalic-polydactyl (hpy) mutation is a recessive, pleiotropic mutation affecting mouse development.
• Homozygous hpy animals exhibit growth retardation and neurological abnormalities.

Purpose of the Study:

• To investigate the pathological mechanisms underlying the hydrocephalic-polydactyl (hpy) mutation.
• To characterize the effects of the hpy mutation on brain development and cellular structures.

Main Methods:

• Light microscopy of serial brain sections.
• Scanning electron microscopy.
• Histological studies.
• Intracerebral tracer dye injections.

Main Results:

• Homozygous hpy mice showed significantly reduced body and brain weight gain from birth to 40 days.
• Mild to severe dilation of the entire ventricular system and ependymal cell damage were observed.
• Ependymal cells were reduced in number, with destruction over large areas; erythrocytes and phagocytes were associated with the ependymal surface.
• No obstruction or stenosis of the aqueduct of Sylvius was detected.
• Neurons appeared normal in number and development compared to wild-type littermates.

Conclusions:

• The hpy mutation leads to hydrocephalus and polydactyly, characterized by ventricular dilation and ependymal damage.
• Despite severe ventricular abnormalities, neuronal development is not overtly affected in hpy homozygotes.
• The hpy mutation's effects are primarily on the ventricular system and ependyma, impacting overall brain growth.