Study #4: Appaloosa Spotting + Pigment Density Regulator (Bl)

This study looks at how the Pigment Density Regulator (Bl) interacts with Appaloosa Spotting and different Base Colors. 

Study #4: 9yo Chestnut Appaloosa
(e/e, A/A, f/f, p/p, LP/-, PATN1/-, Vrn/-)

Chestnut + Pigment Density Regulator (Bl)

No Darkening Genes	HET Sooty	HOM Sooty
No Bl	No Bl + Sty/-	No Bl + Sty/Sty
Bl/-	Bl/-, Sty/-	Bl/-, Sty/Sty
Bl/Bl	Bl/Bl, Sty/-	Bl/Bl, Sty/Sty

Of the nine images above, all of them except the very last one (Bl/Bl, Sty/Sty) showed any shade changes. In this case, Bl/Bl, Sty/Sty was the same as Bl/-, Sty/Sty. Spot Size only changed with the addition of Sooty, it did not change with Bl. 

HET DP	HOM DP	Sooty + DP
No Bl + DP/-	No Bl + DP/DP	No Bl + Sty/-, DP/DP
Bl/-, DP/-	Bl/-, DP/DP	Bl/-, Sty/Sty, DP/DP
Bl/Bl, DP/-	Bl/Bl, DP/DP	Bl/Bl, Sty/Sty, DP/DP

This test saw less Shade variation, specially when the Darkening Genes were Homozygous. At some point the Pigment Density Regulator can only deepen the Base color so much. With Sty and DP were combined with Bl, there was no change in Shade or Varnish. 

Pigment Density Regulator (Bl) on Other Colors

Bay + No Bl	Bay + Bl/ and Bay + Bl/Bl
Black + No Bl	Black + Bl/ and Black + Bl/Bl

Pigment Density Regulator altered Bay ever so slightly, but it can be mostly seen in the reduced Varnishing. The expression did not change between HET Bl and HOM Bl. Unlike with DP and Sty, Bl does not change Black Based horses. The Varnish expression stayed the same. Like with Chestnut, Pigment Density Regulator did not change Spot Size. 

Final Observations

1. Pigment Density Regulator deepens Red Pigment, and can change Chestnut and Bay horses.
2. It has a stronger influence on Chestnut base. 
3. Even though it darkens the coat color, it does not change Spot Size. 
4. Expression of Appaloosa Varnish will be reduced with Pigment Density Regulator.