Fin growth control

Although the major structures of animals are determined early in embryogenesis, morphology can change considerably during post-embryonic development. Variation in adult form in particular plays an important role in processes such as sexual selection and speciation. The body proportions of an organism can easily be modified, as different body parts grow at different rates. This process is referred to as allometric growth. In humans, for example, the head grows at a slower rate than limbs, resulting in a change of head to body proportions between newborns and adults. Differential growth can also lead to pathological conditions such as acromegaly, a syndrome characterised by post-pubertal enlargement of head, hands and feet.

 In order to understand the genetic basis of organ growth and size control, we performed a forward genetic screen specific for adult phenotypes. Several mutants displaying fin overgrowth were iso­lated. While some of our mutants show general fin overgrowth as well as overgrown barbels, others exhibit overgrowth only in the dorsal fin. In teleost fish, fins are composed mainly of a skeleton of segmented rays covered by skin. Anatomical analysis of our mutants revealed that an increment in fin size can be achieved either by increasing the amount of segments composing the fin ray or by elongation of the segments themselves.

 We are currently aiming to find the genetic basis underlying fin overgrowth through a positional cloning approach. Additionally, we would like to take advantage of transgenesis techniques to assess which biological mechanisms are implicated in organ growth and size control and to which extent this phenomenon correlates to processes such as cancer.

Fig. 1: Wild type (+/+) zebrafish and different fin mutants. All the mutants depicted are dominant. Note the barbel overgrowth in Pfau and Schleierschwanz (Ssz) mutants, as well as the pigmentation phenotype in homozygous Schleierschwanz (Ssz/Ssz).

Personnel involved

Simon Perathoner           PhD student      (05/08 – present)

Ines Gehring                    Technician         (05/08 – 12/09)

Dr. Matthew Harris           Postdoc             (Harvard Medical School, Boston, USA)

Collaborators

Ulrike Henrion                  Postdoc             (IKE, Linköping, Sweden)

Katja Steinke                    PhD student      (RUB, Bochum, Germany)

Guiscard Seebohm        Professor           (RUB, Bochum, Germany)