Identification of PINK1 in the brain, eye and ear of mouse during embryonic development.

PINK1 is a 581 amino acid protein with a serine/threonine kinase domain and an N-terminal mitochondrial targeting motif. The enzyme is expressed in the brain as well as in several tissues such as heart, skeletal muscle, liver, kidney, pancreas and testis. In the present study, we have investigated by Western blot analysis and immunohistochemistry the presence and distribution of PINK1 in the brain, eye and inner ear of mouse during embryonic development. In the brain we detected a PINK1 molecular form of 66 kDa. Immunoreactive perikarya first appeared at stage E15 in the diencephalon within the thalamus, the hypothalamus, the periventricular layers of the third ventricle and in the rhombencephalon at level of the pons. Subsequently, new PINK1-positive neurons were found in the midbrain within the floor and the periventricular layers of the ventral wall of the mesencephalic vesicle (stage E17) as well as in the neopallial cortex, the tegmentum of the midbrain and the periventricular region of the caudal part of the rhombencephalon (stage E19). At P0, PINK1-immunoreactive cells appeared in the striatum, the mantle layer and caudal part of the medulla oblongata and the cerebellum. The spatio-temporal expression of PINK1 and its heterogeneous distribution suggest that the enzyme might be involved in neuroregulatory processes during embryogenesis. In the eye, PINK1-immunoreactivity was found in lens and in the cornea, whereas in the inner ear the enzyme was expressed in the ependymal and subependymal cells of the saccule and in the semicircular canals indicating that PINK1 plays a role in the development of these sensory organs.