Bisalbumineamia in a bottlenosed dolphin (Tursiops truncatus)

Mutations and polymorphism in bottlenose dolphin (Tursiops truncatus, Montagu 1821) albumin gene: First identification of mutations responsible for inherited bisalbuminemia

Hereditary bisalbuminemia is an asymptomatic and heterozygous condition in a range of species characterized by the presence of two serum albumin fractions with different electrophoretic mobility resulting in a bicuspid pattern on serum electrophoresis. Bisalbuminemia has been diagnosed by electrophoresis in two bottlenose dolphin (Tursiops truncatus) families, but causative mutations and the inheritance pattern have not been identified. The aims of this work are: to investigate polymorphisms of the bottlenose dolphin albumin gene and to identify mutations causative of bisalbuminemia; to identify the inheritance pattern in two bottlenose dolphin families. Coding regions of the albumin gene were screened for mutations in 15 bottlenose dolphins kept under human care from two distinct families. Eighteen albumin mutations (three synonymous and 15 non-synonymous) were identified. Two non-synonymous variations co-segregated with bisalbuminemic phenotype: p.Phe146Leu in exon 4 and p.Tyr163His in exon 5. The amino acid change in exon 5 was associated with the secondary and/or tertiary structure variation of the protein and has been reported as causative of bisalbuminemia in humans. Pedigree analysis of the dolphin families showed an autosomal codominant inheritance pattern. In this work, the mutations potentially responsible for bisalbuminemia were identified and confirmed the autosomal codominant trait in bottlenose dolphins.

Detection of hereditary bisalbuminemia in bottlenose dolphins (Tursiops truncatus, Montagu 1821): comparison between capillary zone and agarose gel electrophoresis

Background

Hereditary bisalbuminemia is a relatively rare anomaly characterized by the occurrence of two albumin fractions on serum protein separation by electrophoresis. In human medicine, it is usually revealed by chance, is not been clearly associated with a specific disease and the causative genetic alteration is a point mutation of human serum albumin gene inherited in an autosomal codominant pattern. This type of alteration is well recognizable by capillary zone electrophoresis (CZE), whilst agarose gel electrophoresis (AGE) not always produces a clear separation of albumin fractions. The aims of this study is to report the presence of this abnormality in two separate groups of related bottlenose dolphins and to compare the results obtained with capillary zone and agarose gel electrophoresis.

Results

Serum samples from 40 bottlenose dolphins kept under human care were analyzed. In 9 samples a double albumin peak was evident in CZE electrophoresis while no double peak was noted in AGE profile. Since only an apparently wider albumin peaks were noted in some AGE electrophoretic profiles, the ratio between base and height (b/h) of the albumin peak was calculated and each point-value recorded in the whole set of data was used to calculate a receiver operating characteristic curve: when the b/h ratio of albumin peak was equal or higher than 0.25, the sensitivity and specificity of AGE to detect bisalbuminemic samples were 87 and 63 %, respectively. The bisalbuminemic dolphins belong to two distinct families: in the first family, all the siblings derived from the same normal sire were bisalbuminemic, whereas in the second family bisalbuminemia was present in a sire and in two out of three siblings.

Conclusions

We report for the first time the presence of hereditary bisalbuminemia in two groups of related bottlenose dolphins identified by means of CZE and we confirm that AGE could fail in the identification of this alteration.