Maine Coon renal screening: ultrasonographical characterisation and preliminary genetic analysis for common genes in cats with renal cysts

Cross-Species Insights into Autosomal Dominant Polycystic Kidney Disease: Provide an Alternative View on Research Advancement

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a prevalent hereditary disorder that affects the kidneys, characterized by the development of an excessive number of fluid-filled cysts of varying sizes in both kidneys. Along with the progression of ADPKD, these enlarged cysts displace normal kidney tissue, often accompanied by interstitial fibrosis and inflammation, and significantly impair renal function, leading to end-stage renal disease. Currently, the precise mechanisms underlying ADPKD remain elusive, and a definitive cure has yet to be discovered. This review delineates the epidemiology, pathological features, and clinical diagnostics of ADPKD or ADPKD-like disease across human populations, as well as companion animals and other domesticated species. A light has been shed on pivotal genes and biological pathways essential for preventing and managing ADPKD, which underscores the importance of cross-species research in addressing this complex condition. Treatment options are currently limited to Tolvaptan, dialysis, or surgical excision of large cysts. However, comparative studies of ADPKD across different species hold promise for unveiling novel insights and therapeutic strategies to combat this disease.

PKD1 gene mutation and ultrasonographic characterization in cats with renal cysts

Background

Polycystic kidney disease (PKD) has a complex phenotype partly explained by genetic variants related to this disease. Ultrasonography is a promising approach for defining clinical signs. This study aimed to assess kidney characteristics in cats with Polycystin-1 (PKD1) gene mutations and wild-type cats. Kidney characteristics were identified by ultrasonography.

Methods

A total of 108 cats of variable breeds aged an average of 37.01±3.50 months were included. Blood examination and biochemical tests were evaluated. For cystic formation, renal ultrasound was performed. The PKD1 gene mutation was identified via polymerase chain reaction (PCR) and DNA sequencing. Matrix correlation and effectiveness of ultrasound for PKD1 mutation detection were determined.

Results

The results showed that 19.44% of cats had PKD1 mutations, a high prevalence in Persian and Persian-related breed cats. Our results demonstrated the characteristics of kidneys in wild-type cats and cats with gene mutations. Based on ultrasonography results, there was an association between cats with gene mutations and cyst formation. The findings indicated that ultrasound did not detect cysts in cats aged 4-36 months, supporting the evidence that PKD1 gene mutations may not be present. This study found high sensitivity and renal specificity ultrasound for PKD1 heterozygous mutation. Moreover, cystic formation via renal ultrasound showed an increased risk for PKD1 mutation 2,623 times compared to normal kidneys.

Conclusions

Ultrasonographic examination, coupled with genetic investigations, may help to clarify the phenotypic variability of PKD1. The phenotypic profile of PKD1 will guide therapeutic outcomes and reduce the prevalence of PKD morbidity and mortality in cats.

Large-scale epidemiological study on feline autosomal dominant polycystic kidney disease and identification of novel PKD1 gene variants

OBJECTIVES

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited disease in cats. In most cases, the responsible abnormality is a nonsense single nucleotide polymorphism in exon 29 of the PKD1 gene (chrE3:g.42858112C>A, the conventional PKD1 variant). The aim of this study was to conduct a large-scale epidemiological study of ADPKD caused by the conventional PKD1 variant in Japan and to search for novel polymorphisms by targeted resequencing of the PKD1 using a next-generation sequencer.

METHODS

A total of 1281 cats visiting the Veterinary Medical Center of the University of Tokyo were included in this study. DNA was extracted from the blood of each cat. We established a novel TaqMan real-time PCR genotyping assay for the conventional PKD1 variant, and all cases were examined for the presence of this variant. Targeted resequencing of all exons of the PKD1 was performed on the DNA of 23 cats with the conventional PKD1 variant, six cats diagnosed with cystic kidneys but without this variant, and 61 wild-type normal cats.

RESULTS

Among the 1281 cats examined in this study, 23 (1.8%) harboured the conventional PKD1 variant. The odds of having the conventional PKD1 variant were significantly higher in Persian cats, Scottish Folds and Exotic Shorthairs than in the other breeds, although the number of cases in each breed was small. Furthermore, we identified four variants unique to cats with cystic kidneys that were not found in wild-type normal cats, all of which were in exon 15. In particular, two (chrE:g.42848725delC, pGly1641fs and chrE:g.42850283C>T, pArg2162Trp) were candidate variants.

CONCLUSIONS AND RELEVANCE

This study revealed that the conventional PKD1 variant was prevalent in Scottish Fold, Persian and Exotic Shorthair breeds in Japan, and variants in exon 15 of PKD1, in addition to the conventional variant in exon 29, would be key factors in the pathogenesis of ADPKD in cats.

Feline Polycystic Kidney Disease: An Update

Polycystic kidney disease (PKD) is a disease that affects felines and other mammals, such as humans. The common name is autosomal dominant polycystic kidney disease (ADPKD) and causes a progressive development of fluid-filled cysts in the kidney and sometimes in other organs as the liver and pancreas. The formation and growth of cysts progress slowly, causing deterioration of kidney tissue and a gradual decrease in kidney function, leading to irreversible kidney failure. Feline PKD or ADPKD in humans are hereditary pathologies of autosomal dominant transmission. ADPKD is one of the genetic diseases with the highest prevalence in humans. In cats, this disease also has a high prevalence, mainly in the Persian breed, being one of the most common feline genetic diseases. Imaging tests seem to be the most reliable method for diagnosis of the disease, although more genetic tests are being developed to detect the presence of the responsible mutation. In this review, we summarize the current knowledge about feline PKD to guide future research related to an adequate diagnosis and early detection of causal mutations. It can allow the establishment of selection programs to reduce or eliminate this pathology in feline breeds.

Feline abdominal ultrasonography: what's normal? what's abnormal? The kidneys and perinephric space

PRACTICAL RELEVANCE

Abdominal ultrasound plays a vital role in the diagnostic work-up of many cats presenting to general and specialist practitioners. Ultrasound examination of the kidneys and perinephric space can provide important information on several conditions including chronic renal disease, hydronephrosis and perinephric pseudocyst formation.

CLINICAL CHALLENGES

Despite ultrasonography being a commonly used modality, many practitioners are not comfortable performing an ultrasound examination or interpreting the resulting images. Even for the experienced ultrasonographer, differentiating between incidental findings, such as a medullary rim sign, and pathological changes can be challenging.

AIM

This review, part of an occasional series on feline abdominal ultrasonography, discusses ultrasonographic examination of the normal and diseased kidney and perinephric space. Aimed at general practitioners who wish to improve their knowledge of and confidence in feline abdominal ultrasound, this review is accompanied by high-resolution images and videos available online as supplementary material. A subsequent article will address ultrasonography of the collecting system including the renal pelvis and urinary bladder.

EQUIPMENT

Ultrasound facilities are readily available to most practitioners, although use of ultrasonography as a diagnostic tool is highly dependent on operator experience.

EVIDENCE BASE

Information provided in this article is drawn from the published literature and the author's own clinical experience.

Epidemiological evaluation of cats associated with feline polycystic kidney disease caused by the feline PKD1 genetic mutation in Japan

Feline polycystic kidney disease (PKD), an inherited autosomal dominant disease, has been reported to occur mostly in Persian or Persian related cats, and to be associated with a mutation from C to A at position 10063 in exon 29 of the feline PKD1 gene (PKD1 mutation). Many clinical cases have been recognized in Japan, but the mutation rate in cats has not been reported. The objective of this study was to determine epidemiological characteristics and clinical features in cats with the PKD1 mutation. Referring veterinarians sent blood samples of 377 cats for the PKD1 gene evaluation. The blood samples were from 159 cats with renal cysts confirmed by ultrasonography, 60 cats without renal cysts, and 158 cats that did not undergo ultrasonography. In total, 150 cats carried the PKD1 mutation and the signalment, site and number of renal cysts, and results of blood test were evaluated in cats with the PKD1 mutation. The breeds with the highest rate of the PKD1 mutation were Persian (46%), Scottish Fold (54%) and American Shorthair cats (47%). However, mixed breed cats also showed high rates of the PKD1 mutation. Of cats with the mutation, the incidence of high plasma creatinine (≥1.6 mg/dl) was greater in cats ≥3 years old, although a few cats ≥9 years of age had low plasma creatinine (<1.6 mg/dl). The coincidence of renal and hepatic cysts was 12.6%, with the high prevalence in Persian cats (31%).