I have been trying to figure out what causes “red” in red fawn french bulldogs and cherry tan french bulldogs.
I’m no scientist but I do enjoy genetics. I’ve been looking into dna of different dogs with these dark tan points such as doberman and rottweiler (rotties have various levels of tan as well), but have come up short with information.
After combining information from various genetic testing sites, I believe I have FINALLY figured it out and put the puzzle together- Intensity Dilution Gene
It’s just a theory(that makes sense), so take this article with a grain of salt.
Table of Contents
Genetics Explained with VCA and UC Davis
Here we’re referring to a few genetic sites VCA and UC Davis.
Melanocytes are the cells within the hair follicles that add melanin to the hair as it grows and determine basic coat color.
The more melanin, the darker the color.
Melanin is not always produced at a steady rate, so the tip of a dog’s hair may be darker than the rest of the hair shaft. For example – Sable Dogs
Each of the pigments, eumelanin and phaeomelanin, has a “default” color that can be modified by various genes.
Black
Eumelanin is, by default, black pigment, but variation in color occurs because genes modify eumelanin to create other colors such as liver/rojo (brown), blue (grey), lilac(silver), or isabella (pale brown).
Genes essentially “dilute” the pigment into these other colors by preventing the production of full strength eumelanin.
In fawns and sables these colors whether black or diluted can present on the tips of the hairs and on the face. In tan pointed and solid dogs these colors are full body.
Fawn
Phaeomelanin is the second pigment that determines canine coat color.
This pigment is red with a default color of gold or yellow.
Phaeomelanin creates reds that range from deep red to orange, cream, gold, yellow, or tan.
Genes control the intensity of phaeomelanin, making the color stronger or weaker.
This pigment is produced only in the coat and affects only hair color, while eumelanin affects eye and nose color.
Eumelanin and phaeomelanin in all their forms create a huge range of dog coat colors.
A Locus-
Responsible for Fawn, Sable, Wild, Saddle(looks like a beagle), Black Back (Black and Tan), and Recessive Black(solid)
The Agouti Signaling Protein (ASIP) gene, also referred to as the A locus, controls where and when eumelanin (black or brown pigment, or their respective dilutions) and phaeomelanin (red or yellow pigment, or their respective dilutions) is produced in the coat of most mammals, including dogs.
The Agouti protein does this by interacting with the melanocortin 1 receptor (MC1R – e locus) to cause a switch in pigment deposition, from the dark eumelanin pigment to the lighter phaeomelanin pigment, in the hair shaft at different stages of hair growth.
Fawn – EE (black- does not express, does not alter tan points )
Fawn Black Mask- EM E or EM e (only expresses on the muzzle, tan points still express)
Fawn Covered in Cream – ayay ee (total coverage of fawn and other a locus)
Sable – Ayat with EE or Em
Solid – aa, no tan whatsoever
Black Mask with Tan Points, EE with tan points, Black Masked Fawn
https://vgl.ucdavis.edu/test/agouti-dog https://vcahospitals.com/know-your-pet/genetics-basics-coat-color-genetics-in-dogs
Intensity Dilution
Mammals produce two kinds of pigment: eumelanin (black and/or brown in color) and phaeomelanin (red and/or yellow in color).
Many genes contribute to the type and amount of pigment produced.
Several breeds of dogs have an extreme dilution phenotype that has been shown to only affect the red pigment phaeomelanin (a locus – fawn and tan points).
Exceptions:
Population studies demonstrate that 10% of dogs homozygous (2 copies) for the In allele do not express extreme dilution.
10% of extreme dilution expressing dogs do not have two copies of the In allele.
Additionally, roughly 2% of dogs with 0 or 1 copies of the In variant will express the extreme dilution
Taken together, these results suggest the phenotype may be impacted by variants at additional genes. These additional genes are currently unknown.
How the gene acts and test results:
Phenotype: Red and yellow pigment is diluted to cream or white hair. Black and brown pigment, if present, will remain undiluted.
Dogs with the N/N genotype are not likely to show the extreme dilution phenotype and cannot transmit the intensity dilution variant to their offspring.
Dogs with the N/In genotype are carriers and likely will not show extreme dilution of phaeomelanin(a locus). They are predicted to transmit the variant to 50% of their offspring, and 25% of pups produced by breeding of two carriers are predicted to have the extreme dilution phenotype caused by the intensity allele.
Dogs with the In/In genotype have two Intensity dilution variants and will likely show dilution of phaeomelanin(a locus) resulting in a cream to white phenotype. They will transmit the variant to all of their offspring.
https://vgl.ucdavis.edu/test/intensity-dog
Cherry Tan French Bulldog
SO in my theory, if we have a dog like our Osiris for example who’s dna is:
at/at D/d n/Co B/b em/em i/i
We know he’s just standard black and tan with black mask. He does NOT have cherry tan points.
Looking at Tucker a Lilac Tan with this dna:
at/at co/co d/d em/e B/b – we didn’t test intensity, but Im willing to bet there’s 2 copies
The dog does not have cherry tan points.
Then we look at Rolo, Black Tan, son of Osiris with this dna:
at/a n/co D/d em/e B/B – also didn’t test intensity but since Osiris carries 2 copies, Rolo automatically has 1 copy, showing little to no dilution of a locus tan points.
Notice that all 3 dogs carry coco, two carry cream, and 2 carry testable chocolate.
Cream: Rolo Tucker
Coco: Rolo, Tucker, Osiris
Testable Chocolate b: Tucker, Osiris
All 3 genes needing 2 copies to express. Intensity can mildly affect with 1 copy, but intense dilution only happens with 2 copies.
I do not have any red fawn french bulldogs in my program
Dogs with Dilution and express colors such as Blue, Lilac, Rojo, Isabella CAN have cherry points
all 3 of these dogs carry coco and cream, with only one NOT carrying testable chocolate “b”. None of them were tested for intensity.
The 4th dog was tested for intensity and he carries 1 copy.
Cherry Tan Points and Red Fawn French Bulldogs Based on DNA and Theory
Although we don’t know for sure what else influences a red fawn french bulldog or Cherry Tan points, with this information we can come to the conclusion that cherry tan points and red fawn french bulldogs only carry 1 or No copies of the intensity dilution gene.
There may be other genes that influence cherry tan points as stated above but research still hasn’t been able to link other genes to these colors.
