The effect of Duchenne Muscular Dystrophy on Purkinje cell number in the mdx mouse

Benjamin Sim & Caroline Rae

Tuesday, March 29th, 2011

Benjamin Sim
Sixth Year Medicine
University of New South Wales

Prof. Caroline Rae
Professor of Brain Sciences, University of New South Wales
Conjoint Senior Principal Research Fellow, Neuroscience Research Australia

Benjamin undertook this research project in the third year of his study at the University of New South Wales. He is currently based at Sutherland hospital (Caringbah) during the final year of his training as a medical student.

Prof. Rae is a biochemist with a background in magnetic resonance and interdisciplinary brain research. She has a great interest in combining different research approaches to study the brain.

Figure 1. Comparison of Nissl stained and Calbindin-D28k immunostained sections. (a) Calbindin immunopositive PCs clearly visible along the PC layer. (b) PCs not visible in Nissl stained section.

Background: Duchenne muscular dystrophy (DMD) is an X-linked recessive disease which causes skeletal muscle wasting in males, resulting in premature death during their early to mid 20s. Males with DMD carry defects in the gene encoding for dystrophin, a protein important in ensuring sarcolemmal stability. Dystrophin has also been implicated in disruption to Purkinje cells in the cerebellum. This disruption to cerebellar Purkinje cells has been proposed to be involved in reducing the IQ of affected boys. Aim: To compare Purkinje cell number and distribution in mutant mdx and normal mice. Methods: Cerebellar slices from both mutant (n=4) and normal (n=4) mice were prepared and stained. The number of Purkinje cells in each slice was estimated by three different cell counting techniques. Counting methods were as follows: firstly, the actual number of Purkinje cells per lobe; secondly, a randomised estimate where five random sections of the Purkinje cells layer were selected, counted and averaged; thirdly, an estimated maximum possible count, where three segments from the Purkinje cell layer with the highest density of cells were used to estimate Purkinje cell population. Results: No statistical significance in Purkinje cell numbers between the two groups was found. However, there was a trend towards a decrease in the median number of Purkinje cells in the mutant group, particularly in lobules 3, 4/5, 6 and 10. Conclusion: The study findings suggest a decrease in Purkinje cell number in mdx mice. The small sample size of this study precludes definitive statistical analysis of Purkinje cell numbers in either group. These findings demonstrate a need for larger mouse-model studies to accurately assess differences in cell numbers between the two groups. Given that the greatest difference in cell numbers was demonstrated in lobules 3 and 4/5, the authors suggest that DMD may affect the cerebellum during the maturation of these lobules. Importantly, a reduced Purkinje cell population may be implicated in the intellectual morbidity in boys with DMD.