Difference between revisions of "Genetic Health Defects"

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== Genetic Health Defects in Rabbits ==


==Charlie color has been tied to megacolon in rabbits==
Rabbits carry several breed-specific genetic mutations that can predispose them to health issues. Some of these are linked to coat color, body size, or skull morphology. Understanding these defects is essential for breeders and veterinarians to minimize suffering and avoid propagating deleterious traits.


Rabbit Genetic Resources Can Provide Several Animal Models to Explain at the Genetic Level the Diversity of Morphological and Physiological Relevant Traits
==Charlie Color and Megacolon==
by Luca FontanesiORCID
Department of Agricultural and Food Sciences, Division of Animal Sciences, University of Bologna, Viale Giuseppe Fanin 46, 40127 Bologna, Italy
Appl. Sci. 2021, 11(1), 373; https://doi.org/10.3390/app11010373
Received: 6 December 2020 / Revised: 27 December 2020 / Accepted: 28 December 2020 / Published: 2 January 2021
(This article belongs to the Special Issue Rabbit Models for Translational Medicine)
https://www.mdpi.com/2076-3417/11/1/373


3.6. The KIT Gene is Responsible for the English Spotting Locus and the Megacolon Defect in the Checkered Giant Breed
The KIT gene, responsible for the English spotting locus, is linked to both coat color patterns and congenital megacolon in Checkered Giant rabbits.
A dominant allele (En) is considered the determining genetic factor for the spotted phenotype, very variable in extent, attributed to the English spotting locus. The recessive wild-type allele (en) determines a self-colored phenotype [81]. Rabbits with the heterozygous genotype En/en have far larger patches of colored fur than rabbits with the homozygous En/En genotype [30]. Heterozygous En/en rabbits have the characteristic spotted patterns described in the English spot (or spotted), Butterfly, and Checkered Giant breeds [67]. This is a unique allelic combination that is needed to produce breed standards desired by fancy breeders. The patches of the spotted phenotypes can be of different colors according to the allelic combination at other loci. Other genes are probably involved in determining the degree of extension of the colored patterns versus the white areas [82]. Dominant homozygous En/En rabbits are affected by an underlying megacolon defect and are usually subvital compared to the animals with the other two genotypes, i.e., En/en and en/en [30,82,83,84,85,86,87]. The defect has incomplete penetrance, it is influenced by environmental factors (age, diet, stressors) and is recessive, as En/en rabbits are not affected [87]. Etiopathogenetic analyses of rabbits having this megacolon pointed out that abnormalities of the enteric nervous system throughout the colon might be involved in this defect [85,86,88].
Several genes that are implicated both in coat color spotted patterns and in similar disfunctions of the digestive tract have been described in rodents and other mammals. Two of these genes were also investigated in association studies with the coat color and megacolon phenotypes in rabbits. The endothelin receptor B (EDNRB) gene was first excluded to be involved in these traits in Checkered Giant rabbits [89]. Subsequently, the analysis of KIT gene markers in Checkered Giant families indicated that a synonymous polymorphism in exon 5 of this gene is associated with both traits [87]. The KIT gene encodes the mast/stem cell growth factor receptor that is mainly involved in the differentiation of melanoblasts and in regulating their migration from the neural crest along the dorsolateral pathway to reach the final destinations in the skin [90,91]. KIT gene expression in the gut musculature is prominent only in interstitial cells of Cajal (ICC) that are essential in gut motility [92]. KIT gene expression in cecum and colon specimens of En/En rabbits resulted very low compared to the expression in the same tissues observed in en/en rabbits. Reduced and altered c-kit immunolabelled ICC, together with neuronal and ICC abnormalities in cecum and colon tissues, were identified in En/En rabbits [87]. Therefore, in addition to the effect of the English spotting locus on a coat color spotted phenotype evidenced in Checkered Giant rabbits, the neuro-ICC changes in rabbits with En/En genotype are reminiscent of the human non-aganglionic megacolon [87]. Therefore, En/En rabbits might be considered as new animal models for this type of defect in humans [87]. The complete sequence characterization of the rabbit KIT gene and of the upstream and downstream regions is needed to identify the causative mutation(s) of the coat color pattern and of the megacolon defect described in this model. Other coat color patterns might have additional variants affecting the KIT gene.
https://www.researchgate.net/publication/261742401_The_KIT_Gene_Is_Associated_with_the_English_Spotting_Coat_Color_Locus_and_Congenital_Megacolon_in_Checkered_Giant_Rabbits_Oryctolagus_cuniculus


==Double [https://mmcrabbits.com/BCWiki/index.php/Dwarf Dwarf Genes] cause Peanuts==
* **Genetics:** 
  * Dominant allele En produces the spotted phenotype; homozygous En/En rabbits are affected by megacolon. 
  * Heterozygous En/en rabbits display standard spotted patterns without megacolon.
  * Wild-type en/en rabbits are self-colored and unaffected.


* **Pathophysiology:** 
  * KIT gene expression in the gut, particularly in interstitial cells of Cajal (ICC), is crucial for gut motility. 
  * En/En rabbits show reduced ICC numbers and abnormalities in cecum and colon tissues, resulting in chronic constipation and megacolon. 


* **Clinical relevance:** 
  * Megacolon in En/En rabbits resembles human non-aganglionic megacolon, making them a valuable model for research. 
  * Incomplete penetrance means environmental factors like diet, age, and stress can influence severity. 


*Reference:* Fontanesi, L. (2021). *Rabbit Genetic Resources Can Provide Several Animal Models to Explain at the Genetic Level the Diversity of Morphological and Physiological Relevant Traits.* Appl. Sci. 11(1):373. https://doi.org/10.3390/app11010373 


Identification and analysis of the dwarf mutation in ...
==Dwarf Genes and "Peanuts"==


Epsilon Archive for Student Projects
* **Double dwarf mutation:** 
https://stud.epsilon.slu.se › hu_d_140622
  * Rabbits homozygous for the dwarf allele often produce nonviable kits, known as "peanuts," due to severe developmental defects. 
PDF by D Hu · 2014
  * Heterozygous rabbits appear normal but can transmit the trait to offspring.   


https://stud.epsilon.slu.se/6908/11/hu_d_140622.pdf
*Reference:* Hu, D. (2014). *Identification and analysis of the dwarf mutation in rabbits.* Epsilon Archive for Student Projects. https://stud.epsilon.slu.se/6908/11/hu_d_140622.pdf


==Max Factor genes Netherland Dwarf breed, causes deformed kits born with open eyes==
==Max Factor Genes in Netherland Dwarfs==
==[https://mmcrabbits.com/BCWiki/index.php/Malocclusion Malocclusion ]==
==Sore Hocks : narrow feet thin fur padding==
________________________________________________


==Netherland dwarf skull myth==[[https://mmcrabbits.com/BCWiki/index.php/Netherland_dwarf_skull_myth]]
* **Effect:** 
  * Certain alleles in Netherland Dwarf rabbits result in kits born with open eyes and craniofacial deformities. 
  * These genetic variants contribute to early neonatal mortality and malformations. 
 
==Malocclusion==
 
* Misaligned teeth can result from inherited jaw or skull morphology defects. 
* Leads to overgrown incisors, dental pain, difficulty eating, and secondary gastrointestinal stasis. 
 
==Sore Hocks==
 
* Predisposition in breeds with narrow feet and thin fur padding. 
* Results in ulceration of plantar surfaces, chronic pain, and secondary infections if untreated. 
 
==Netherland Dwarf Skull Myth==
 
* Many claims about extreme skull shape in Netherland Dwarfs causing health problems are exaggerated. 
* Morphological variation exists, but careful breeding can mitigate associated risks. 
 
==References==
* Fontanesi, L. (2021). Rabbit Genetic Resources Can Provide Several Animal Models... *Appl. Sci.*, 11(1):373. https://www.mdpi.com/2076-3417/11/1/373 
* Hu, D. (2014). Identification and analysis of the dwarf mutation in rabbits. Epsilon Archive. https://stud.epsilon.slu.se/6908/11/hu_d_140622.pdf 
* MMC Wiki: [Malocclusion](https://mmcrabbits.com/BCWiki/index.php/Malocclusion) 
* MMC Wiki: [Dwarf Genes](https://mmcrabbits.com/BCWiki/index.php/Dwarf) 
* MMC Wiki: [Netherland dwarf skull myth](https://mmcrabbits.com/BCWiki/index.php/Netherland_dwarf_skull_myth)

Latest revision as of 00:39, 18 August 2025

Genetic Health Defects in Rabbits[edit | edit source]

Rabbits carry several breed-specific genetic mutations that can predispose them to health issues. Some of these are linked to coat color, body size, or skull morphology. Understanding these defects is essential for breeders and veterinarians to minimize suffering and avoid propagating deleterious traits.

Charlie Color and Megacolon[edit | edit source]

The KIT gene, responsible for the English spotting locus, is linked to both coat color patterns and congenital megacolon in Checkered Giant rabbits.

  • **Genetics:**
 * Dominant allele En produces the spotted phenotype; homozygous En/En rabbits are affected by megacolon.  
 * Heterozygous En/en rabbits display standard spotted patterns without megacolon.  
 * Wild-type en/en rabbits are self-colored and unaffected.
  • **Pathophysiology:**
 * KIT gene expression in the gut, particularly in interstitial cells of Cajal (ICC), is crucial for gut motility.  
 * En/En rabbits show reduced ICC numbers and abnormalities in cecum and colon tissues, resulting in chronic constipation and megacolon.
  • **Clinical relevance:**
 * Megacolon in En/En rabbits resembles human non-aganglionic megacolon, making them a valuable model for research.  
 * Incomplete penetrance means environmental factors like diet, age, and stress can influence severity.
  • Reference:* Fontanesi, L. (2021). *Rabbit Genetic Resources Can Provide Several Animal Models to Explain at the Genetic Level the Diversity of Morphological and Physiological Relevant Traits.* Appl. Sci. 11(1):373. https://doi.org/10.3390/app11010373

Dwarf Genes and "Peanuts"[edit | edit source]

  • **Double dwarf mutation:**
 * Rabbits homozygous for the dwarf allele often produce nonviable kits, known as "peanuts," due to severe developmental defects.  
 * Heterozygous rabbits appear normal but can transmit the trait to offspring.

Max Factor Genes in Netherland Dwarfs[edit | edit source]

  • **Effect:**
 * Certain alleles in Netherland Dwarf rabbits result in kits born with open eyes and craniofacial deformities.  
 * These genetic variants contribute to early neonatal mortality and malformations.

Malocclusion[edit | edit source]

  • Misaligned teeth can result from inherited jaw or skull morphology defects.
  • Leads to overgrown incisors, dental pain, difficulty eating, and secondary gastrointestinal stasis.

Sore Hocks[edit | edit source]

  • Predisposition in breeds with narrow feet and thin fur padding.
  • Results in ulceration of plantar surfaces, chronic pain, and secondary infections if untreated.

Netherland Dwarf Skull Myth[edit | edit source]

  • Many claims about extreme skull shape in Netherland Dwarfs causing health problems are exaggerated.
  • Morphological variation exists, but careful breeding can mitigate associated risks.

References[edit | edit source]

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