Abstract
Purpose: :
To investigate the spatial and temporal expression profile of FRMD7 in developing human brain.
Methods: :
Human embryonic and fetal tissue sections were obtained from HDBR (Newcastle) at embryonic stages CS15 (~33dpc) to CS23 (~56dpc) and fetal stage 9 weeks post conception (wpc). For in-situ hybridisation (ISH) studies, sense and antisense probes were generated as we have described in (Tarpey, et al. 2006). Anti-FRMD7 antibodies (1:250, Atlas Antibodies) were used for immunohistochemistry (IHC) studies. Primary culture technique was used to culture postnatal day 1 rat cerebellum followed by immunofluorescence using anti-FRMD7 antibodies.
Results: :
IHC results showed a migratory expression pattern in the developing cerebral cortex between stages CS15 - CS23. Initially the ventricular and subventricular zones (VZ and SVZ) showed strong expression followed by the intermediate zone (IZ) and the cortical plate. Similar results were reported from the ISH studies. At stages CS15, CS16 and CS19 strong hybridisation signals were detected in the trigeminal ganglion. However at 9 wpc IHC showed no expression in the trigeminal ganglion. Both medial and lateral ganglionic eminences (MGE and LGE) showed strong FRMD7 mRNA expression at CS20. Interestingly, at CS23 there was expression in the VZ of the cerebellar peduncle. Moreover, primary culture of rat cerebellum showed strong FRMD7 expression along the axons and dendrites of neuroblastic cells, particularly intensely in large presumable Purkinje cells, with no expression in glial cells.
Conclusions: :
This study highlights the specific oculomotor centres likely to be involved in FRMD7 related infantile nystagmus. Cerebellar involvement may suggest an unstable neural integrator in the patients with mutations. Trigeminal ganglion involvement may suggest the likely origin of a defective sensory signal (within the feedback loop) and how its disruption could be beneficial. Furthermore, MGE and LGE are sources of GABAergic neurons while, in humans, cortical VZ also contributes GABAergic neurons as well as glutamatergic neurons destined for the cortical anlage. This may help explain why treatment with gabapentin and memantine are helpful in these patients.
Keywords: nystagmus • fluorescent in situ hybridization • immunohistochemistry