Untersuchung des CFL-Phänotyps ("congenital fused labia" ) in dem Neuweltaffen Common Marmoset (Callithrix jacchus) unter demographischen, physiologischen und zytogenetischen Gesichtspunkten

Abstract

The theme of this submitted doctoral dissertation is a multiple aspect investigation of the phenotype closed vulva (congenital-fused-labia (CFL) which commonly occurs in young and adult female common marmosets in captivity. This phenotype involves joined Labia majora through a connective tissue and skin fusion in different degrees of severity. In the German Primate Centre Goettingen (DPZ) this phenotype occurs in high frequency. Until the present study there have been very few scientific publication on this theme. From some authors it was suggested that this was a pathological process, which involved a masculinization of females. A further hypothesis was that this phenotype could involve a developmental delay of the genitalia caused by the captive environment. It was the goal of the submitted study, to investigate the causal origins of the CFL phenotype in captive female common marmosets. For this purpose 146 randomly selected female marmosets were investigated from the perspective of genetic, physiological, demographic, and cellular changes associated with this phenotype. The genitalia of these females was quantitatively characterized with a standard measuring system supplemented by photographs to record labial form and color. Based on the measurements, the animals were assigned to 1 of 4 groups based on the degree of closure. To evaluate the genetic and family tree histories, an analysis of the development and origin of the DPZ population was carried out. One of the primary aims was to determine whether the CFL-phenotype had entered the DPZ colony from particular identifiable external colonies. No evidence could be found for this hypothesis in the family tree analysis, suggesting that the possibility of a simple genetic origin for this phenotype was unlikely. In contrast, the physiological and demographic investigations indicated that body weight of the mother as well as the daughter played a critical role in the severity of the phenotype. The hormone analyses also showed a significant correlation between the androstenedione level and the CFL degree as well as with body weight, providing an interrelated set of physiological changes. This showed that the higher the body weight, the higher the androstenedione level and strongly supporting the hypothesis that the CFL phenotype can be interpret! ed as a masculinization of the external genitalia indirectly caused by increased weight through the related changes in hormonal balance. On the sub-cellular/cytogenetic level, an imbalance of the natural chimerism, originating from fetal life and the shared placental circulation which is known to occur naturally in this species, was considered as a further possible cause of masculinization in mixed sex litters. It was hypothesized that through the increased litter sizes produced by the higher weight mothers, (3 or 4 instead of 2 or 1), an individual with an excess of cells from the other sex may occur as a consequence of an unequal sex balance in the litter. The proportion of XY WBC s cells, in females from mixed sex litters were first evaluated using classic cytogenetic methods. Additionally fluorescence-in-situ-hybridization (FISH) techniques for X and Y chromosome genes was developed specific for common marmoset since standard human markers available in clinical kits did not work for this species. The result of this investigation was that females with a higher XY to XX ratio in chimerism also have a higher weight and a higher degree of CFL. The results of this study all point to the importance of high weight and its multiple consequences and the critical role of not only the external environment but also the maternal/uterine environment in determining the fate of the next generation (a kind of epigenetic effect) promoting development of high weight and a partial masculinization of the daughters. Based on the information available to us in the captive population, the CFL phenotype is the normal status for the infant and juvenile common marmoset female. When the labia open in the wild population is unknown, but it can be assumed that CFL phenotype after puberty can be classified as a developmental delay. Our studies have strongly suggested that the labial opening is hindered by the hormonal and physiological changes associated with over-weight in captivity and appears to be first triggered in the uterine environment of the over-weight mothers. Therefore, it can be expected that the longer a marmoset colony has lived under conditions promoting overweight, that the more extreme will be the symptoms in a cumulative fashion over time. The rate of triplet and higher litter sizes gradually increases, along with frequency of imbalanced cross-sex chimerism, progressively more extreme body weights, increased androstenedione levels and frequency of CFL-syndrome in adult females.