From single nucleotide substitutions up to chromosomal deletions: genetic pause of leucism-associated disorders in animals.

Leucism is characterized by a complete or partial white skin and hair in combination with pigmented irides, which can be vivid blue or heterochromatic. This is due to a complete or partial lack of melanocytes. The underlying pathogenesis is a disturbed emigration or differentiation of neural crest-derived cells. Therefore, leucistic phenotypes can be associated with defects, which mainly impair sensory organs and nerves. In humans, a well-known example is the Waardenburg syndrome. Leucism-associated disorders were also described in mouse, rat, hamster, rabbit, mink, cat, dog, pig, sheep, llama, alpaca, cattle and horse. In some of these species already identified causal mutations affect the genes EDN3, EDNRB, KIT, MITF, PAX3, SILV and SOX10. Defect alleles represent different types of genetic variation, ranging from single nucleotide substitutions up to larger chromosomal deletions. Some of the defect alleles produce desired coat color patterns. In some but not all cases, available genetic tests enable breeders to avoid production of animals affected by a leucism-associated disorder.

Síndrome de Waardenburg (S.W.) (distopía cantorum) (displasia interoculo irido dermato auditiva) / Waardernburg syndrome: report of case

The Waardenburg syndrome is a rare genetical disease characterized by skeletal and facial alterations. In this report we present a case of 15 years old girl bearing this syndrome, who was subjected to orthodontic, phonoaudiologic and kinesiologic studies in order to give her a consistent oral rehabilitation and preventive treatment

Genetic diseases of hearing.

The study of genetic hearing loss has always been hindered by the difficulty of separating sporadic genetic cases from cases affected by environmental influences. This is because audiologic methods are largely insensitive to causes, and the anatomical location of the affected structures in the middle and inner ear makes histopathologic verifications difficult. With recent progress in genetic investigation, eg, the mapping of the gene location for the Waardenburg and Usher syndromes, both syndromic and nonsyndromic genotypes have been elucidated in humans and in animal models. In the future, molecular genetics will play an increasingly important role in the genetic counseling of suspected carriers, as well as in the prevention of additional hearing loss from exogenic causes (noise, ototoxic drugs) in confirmed cases of genetically vulnerable ears.