There has been growing discussion among breeders about the ALMS1 gene and its connection to hypertrophic cardiomyopathy (HCM) in Sphynx cats. However, some misunderstandings have arisen, particularly in interpreting the clinical data from a recent study.
The study focused on a relatively small sample of 55 Sphynx cats. While the data offers valuable insights, it’s important to note that conclusions drawn from such a limited sample should be viewed cautiously. Additionally, since HCM is an age-dependent disease, it may not fully develop in all cases during the short follow-up period (just under two years).
Of the cats diagnosed with HCM, 22.7% did not carry the ALMS1 variant, while 76.2% did—either homozygous (13.6%) or heterozygous (63.6%). Despite this, researchers concluded that, because the majority of the Sphynx population carries this mutation, the ALMS1 variant likely has nothing to do with causing HCM.
This conclusion, however, is nothing new. The fact that the majority of Sphynx cats carry this mutation has been well-known for years, as shown in earlier studies. What is new in this study is that, for the first time, researchers have decided to make this mutation irrelevant to HCM due to the widespread nature of the variant.
As a result, some breeders have been advising others to stop ALMS1 testing, suggesting it’s no longer necessary and that efforts should focus on heart scans and outcrossing. This interpretation can lead to misunderstandings. While not every cat with HCM has the ALMS1 variant, a significant majority do, suggesting that this gene could still play a role.
Moreover, no research has ever suggested that ALMS1 alone causes HCM. Genetic conditions like HCM are complex, influenced by multiple genes and environmental factors. It’s important to consider this complexity rather than drawing conclusions from incomplete interpretations.
As a contrast - I came across an insightful study titled Genetic Basis of Hypertrophic Cardiomyopathy in Cats by Dr. Arkadiusz Grzeczka, Dr. Szymon Graczyk, Dr. Robert Pasławski, and Prof. Urszula Pasławska, published in Current Issues in Molecular Biology in August 2024. This research delves into the genetic mutations associated with Hypertrophic Cardiomyopathy (HCM), a common heart condition in cats. After reading the paper, I reached out to Dr. Grzeczka and Prof. Pasławska to further explore the role of the ALMS1 gene in relation to HCM, particularly in Sphynx cats.
According to Dr. Grzeczka, various mutations of the ALMS1 gene have been repeatedly linked to the thickening of the left ventricular wall, a key feature of HCM. What’s more, ALMS1 is intriguingly associated with the Sphynx breed and similar breeds like Devon Rex. In fact, homozygous mutations (two copies of the mutation) are found predominantly in Sphynx cats. However, whether it’s worth testing for these mutations is difficult to answer, as these mutations are widely spread in the cat population, which may indicate a predisposition to HCM in these cats.
Additionally, Dr. Grzeczka noted that ALMS1 mutations are also found in humans and can sometimes lead to dilated cardiomyopathy—a condition more commonly diagnosed in dogs. This connection suggests a potential link between ALMS1 mutations and heart diseases across various species. From an evolutionary perspective, the fact that these mechanisms appear across different species underscores their importance.
Prof. Urszula Pasławska also shared her views on Ki-67, explaining that Ki-67 is a nuclear protein linked to cell proliferation. She stated: “Ponieważ tą proliferację kontroluje, to jest wygodnym markerem stanu nasilenia wzrostu. Wykazano, że HCM jest związany z nasileniem wzrostu. Nie należy jednak traktować Ki-67 jako markera hypertrofii, bo wzrost Ki-67 będzie również obserwowany w przebiegu choroby nowotworowej i przy nasileniu procesów regeneracyjnych.” (“Since it controls proliferation, it is a convenient marker for the intensity of cell growth. It has been shown that HCM is associated with increased cell growth. However, Ki-67 should not be regarded as a marker of hypertrophy, as its increase is also observed in cancer and during regenerative processes.”) Prof. Pasławska emphasized that documenting high levels of Ki-67 in HCM cases is an important sign for veterinarians to consider anti-proliferative therapies, which she has used for the past six years with satisfactory results. However, she added that, as with HCM, this therapy is not always effective in every cat.
Prof. Pasławska also expressed her opinion on genetic testing, stating: “Mimo to uważam, że warto koty testować genetycznie i wybierać do hodowli te, które są wolne od podejrzanych genów. Dlaczego w populacji nowozelandzkiej wyszło inaczej? Nie wiem.” (“Nevertheless, I believe it is worth genetically testing cats and selecting those that are free from suspicious genes for breeding. Why the results in the New Zealand population turned out differently? I don’t know.”)
In conclusion, while genetic testing for ALMS1 in Sphynx cats might not always provide clear answers, its widespread prevalence suggests that it may still be important in understanding the breed’s predisposition to HCM. Both Dr. Grzeczka and Prof. Pasławska agree that sharing more genetic data on cats could significantly advance research and improve health outcomes.
We will continue to test for the ALMS1 variant. Even though we don’t yet fully understand its impact, combining genetic testing with heart scans helps breeders make informed decisions. This also provides crucial information as research progresses and offers an early warning for buyers about potential health risks.
Our goal is transparency and ensuring the health of the breed. It’s also important to mention that all of our cats are clear of ALMS1 mutation.
If you are conducting genetic testing for ALMS1 or have insights into feline genetic health, feel free to connect!
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