Table 2 Summary of testis-epididymis trans-luminal signalling events in rodents and humans

Testicular ligand gene expression satisfying trans-luminal signalling

Nell2/NELL2 and Nicol1/NICOL1 expression

Yes

[9, 10]

Yes

Complex formation

of testicular ligand proteins

NELL2-NICOL interaction

Yes

[10]

Yes

Testicular ligand-epididymal receptor interaction

NELL2-ROS1 interaction

NICOL-ROS1 interaction

Yes

[9, 10]

Yes

NELL2-ROS1 interaction

Epididymal gene expression regulated by testis-epididymis trans-luminal signalling

Epididymal expression of genes regulated by Nell2

Yes

[9]

Unknown, but human orthologs of mouse lumicrine-regulated genes are expressed