The Journal of Neuroscience, September 15, 2002, 22(18):8110-8116
Dissection of the Cellular and Molecular Events that Position
Cerebellar Purkinje Cells: A Study of the math1
Null-Mutant Mouse
Patricia
Jensen1,
Huda Y.
Zoghbi2, and
Dan
Goldowitz1
1 University of Tennessee Health Science
Center, Memphis, Tennessee 38163, and 2 Howard Hughes
Medical Institute, Baylor College of Medicine, Houston, Texas 77030
Granule cell precursors in the external germinal layer (EGL) of the
cerebellum have been proposed to be a major player in the migration and
positioning of Purkinje cells through the expression of the Netrin-like
receptor Unc5h3 and the extracellular matrix molecule Reelin. To
explore the role of the EGL on these processes, we made use of the
math1 null-mutant mouse in which the EGL does not form.
In the absence of the EGL, we find three populations of ectopic
Purkinje cells. First, we find 1% of all Purkinje cells in a
supracerebellar position at the dorsal midline. Second, we find 7% of
all Purkinje cells in the inferior colliculus, similar to what is seen
in the Unc5h3 mutant. Our finding that Unc5h3 expression
is not disrupted in these cells supports the proposed role of EGL
granule cell precursors in establishing the anterior cerebellar
boundary through the expression of Unc5h3. Third, we find 20% of all
Purkinje cells positioned deep to the cerebellar cortex as seen in the
reeler mutant. However, unlike the reeler mutant, where 5% of the Purkinje cells migrate successfully, we find
that in the math1 null that 72% of the Purkinje cells
migrate successfully. This finding demonstrates that Purkinje cell
migration is not solely dependent on Reelin signaling from the EGL and
is likely caused by Reelin signals emanating from the nuclear
transitory zone or the ventricular zone, or both.
Key words:
Math1; Reelin; Disabled-1; Unc5h3; migration; EGL; granule cell
Copyright © 2002 Society for Neuroscience 0270-6474/02/22188110-07$05.00/0