D. Sanchez et al., Characterization of two novel lipocalins expressed in the Drosophila embryonic nervous system, INT J DEV B, 44(4), 2000, pp. 349-359
We have found two novel lipocalins in the fruit fly Drosophila melanogaster
that are homologous to the grasshopper Lazarillo, a singular lipocalin wit
hin this protein family which functions in axon guidance during nervous sys
tem development. Sequence analysis suggests that the two Drosophila protein
s are secreted and possess peptide regions unique in the lipocalin family.
The mRNAs of DNLaz (for Drosophila neural Lazarillo) and DGLaz (for Drosoph
ila glial Lazarillo) are expressed with different temporal patterns during
embryogenesis. They show low levels of larval expression and are highly exp
ressed in pupa and adult flies. DNLaz mRNA is transcribed in a subset of ne
urons and neuronal precursors in the embryonic CNS. DGLaz mRNA is found in
a subset of glial cells of the CNS: the longitudinal glia and the medial ce
ll body glia. Both lipocalins are also expressed outside the nervous system
in the developing gut, fat body and amnioserosa. The DNLaz protein is dete
cted in a subset of axons in the developing CNS. Treatment with a secretion
blocker enhances the antibody labeling, indicating the DNLaz secreted natu
re. These findings make the embryonic nervous system expression of lipocali
ns a feature more widespread than previously thought. We propose that DNLaz
and DGLaz may have a role in axonal outgrowth and pathfinding, although ot
her putative functions are also discussed.