High impact information on Epha5

• Here we demonstrated with in situ hybridization techniques that mRNA of the Eph receptor tyrosine kinase EphA5 and one of its ligands, ephrin-A5, are present in distinct cortical layers, at a time when intrinsic connections are being formed in the cortex [1].
• Three putative receptors for ephrin-A5 -- EphA3, EphA4 and EphA5 -- showed distinct expression patterns in the developing thalamus [2].
• Ehk-1 and Ehk-2 are almost exclusively expressed in the nervous system [3].
• We show that the ligand ephrin-A3 and the receptor EphA5 are expressed in complementary gradients in the adult rat mossy fiber system [4].
• Taken together these results implicate REK7/EphA5 in the regulation of synaptic plasticity in the mature hippocampus and suggest that REK7/EphA5 activation is recruited in the LTP induced by tetanization [5].

Biological context of Epha5

• Compared to the amino acid sequences of various Eph family members, Ehk-1 and Ehk-2 are closest to the Sek and Cek-4/Mek-4/Hek kinases, and both are more similar to the Elk kinase than they are to the Eck or Eph kinases [3].
• Ehk-1 gene expression is observed in the developing and adult central nervous system and is highly regulated throughout development at both the messenger RNA and protein levels [6].
• We show that a REK7/EphA5 antagonist, soluble REK7/EphA5-IgG, impairs the induction of long-term potentiation (LTP) without affecting other synaptic parameters such as normal synaptic transmission or paired-pulse facilitation [5].
• Bilateral increases in retinal EphA5 expression demonstrate that signals for up-regulation operate interocularly [7].

Anatomical context of Epha5

• The continued expression of REK7/EphA5 in the adult brain, in particular in areas associated with a high degree of synaptic plasticity such as the hippocampus, raises the question of its function in the mature nervous system [5].
• Expression of ephrin-A2 in the superior colliculus and EphA5 in the retina following optic nerve section in adult rat [8].

Associations of Epha5 with chemical compounds

• Ehk-1 and Ehk-2: two novel members of the Eph receptor-like tyrosine kinase family with distinctive structures and neuronal expression [3].

Regulatory relationships of Epha5

• We found that although both EphA5 and its ligands were both expressed by primary olfactory neurons within the embryonic olfactory nerve pathway, there was no graded or complementary expression pattern [9].
• Following unilateral optic nerve section in adult PVG hooded rat, the axon guidance cue ephrin-A2 is up-regulated in caudal but not rostral superior colliculus (SC) and the EphA5 receptor is down-regulated in axotomised retinal ganglion cells (RGCs) [7].

Other interactions of Epha5

• Expression of EphA5 during development of the olfactory nerve pathway in rat [9].
• Results are compared to normal animals in which tectal ephrin-A2 and retinal EphA5 are expressed, respectively, as shallow ascending rostro-caudal and naso-temporal gradients [7].

Analytical, diagnostic and therapeutic context of Epha5

• We performed northern blot analysis for quantification, and found that, three days after injury, the values decreased to 33 +/- 4%, 33 +/- 1% and 46 +/- 1% of control values for TK63 (EphA4), TK25 (EphB2) and TK23 (EphA5), respectively [10].

References