Transverse pigment bars on lavender plumage: What causes it?

[Lindsay Helton]

Here are two articles if you want to read about what is happening from a scientific standpoint.

There is defective peripheral accumulation of melanosomes to the dendrites. This results in the patchy transfer of melanosomes into the keratinocytes of the growing feather. The dilution effect is essentially the result of a mixture of pigmented and unpigmented regions within the feather barbs.

Disruption of a triprotein complex reduces the capacity for melanosome translocation to the periphery of the cell in readiness for transfer to the keratinocytes of the developing feather.

https://bmcgenomdata.biomedcentral.com/articles/10.1186/1471-2156-9-7

Lavender melanocytes, both in vivo and in vitro, produce melanosomes normally but are defective in melanosome translocation. This defect results in a congestion of melanosomes perinuclearly and the absence of dendritic pigment.

In lavender melanocytes prominent pigmentless dendrites emanate from melanosome-congested perikarya. The apparent defect in lavender melanocytes in vivo involves aberrant melanosome distribution. In lavender, melanosomes migrate only as far as the region of dendrite initiation resulting in melanin-congested perikarya and pigment-less dendrites.

In lavender melanocytes, melanosomes fail to move beyond the region of dendrite initiation. Melanosomes are restricted to perinuclear regions in some lavender melanocytes while in others, melanosomes migrate as far as the bases of the dendrites.

In a wild-type melanocyte melanosomes are evenly distributed throughout the cell body and dendrite, and accumulate in the dendritic tip in preparation for melanosome transfer. In a lavender melanocyte melanosomes are restricted to perinuclear regions. The production of melanosomes is normal although their distribution is not.

https://scholar.google.com/scholar_lookup?&title=Lavender%2C%20a%20chick%20melanocyte%20mutant%20with%20defective%20melanosome%20translocation%3A%20a%20possible%20role%20for%2010%20nm%20filaments%20and%20microfilaments%20but%20not%20microtubules&journal=J%20Cell%20Sci&volume=51&pages=25-51&publication_year=1981&author=Mayerson%2CPL&author=Brumbaugh%2CJA#d=gs_qabs&t=1707318319070&u=%23p%3DiAAMiky2i3oJ