[Genetics of oculocutaneous albinism]. / Genetik bei okulokutanem Albinismus.

Albinism comprises a heterogeneous group of nonprogressive genetic disorders characterized by the absence of pigmentation in the skin, hair, and/or eyes. Hypopigmentation or complete lack of pigmentation is caused by an enzyme deficiency involving the production, metabolism, or distribution of melanin. Clinically, oculocutaneous and ocular types, as well as syndromes associated with albinism resulting from mutations in at least 14 genes, are distinguishable. Most frequent is oculocutaneous albinism (OCA), which is subdivided nowadays into four forms, OCA 1-OCA 4. OCA is inherited as an autosomal recessive trait. Clinical differentiation of OCA types is difficult due to the observed range of phenotypic variation. Thus, genetic analysis may be helpful with respect to a precise diagnosis. Sequencing of the four genes associated with OCA detects variations in approximately 60-70% of German patients with albinism. The majority of German patients are affected by OCA 1 resulting from mutations in the gene for tyrosinase, the key enzyme in the synthesis of melanin pigment. Worldwide, OCA2 is the most frequent form of albinism.

Efficient generation of transgenic mice with intact yeast artificial chromosomes by intracytoplasmic sperm injection.

The production of animals with large transgenes is an increasingly valuable tool in biotechnology and for genetic studies, including the characterization and manipulation of large genes and polygenic traits. In the present study, we describe an intracytoplasmic sperm injection (ICSI) method for the stable incorporation and phenotypic expression of large yeast artificial chromosomes (YAC) constructs of submegabase and megabase magnitude. By coinjecting spermatozoa and YACs into metaphase II oocytes, we were able to produce founders exhibiting germline transmission of an intact and functional transgene of 250 kilobases, carrying the mouse tyrosinase locus, used here as a reporter gene to rescue the albinism of recipient mice. More than 35% transgenesis was obtained for this YAC transgene. When compared with the pronuclear microinjection standard method, the efficiency of the ICSI-mediated YAC transfer system was significantly greater. In summary, we describe, for the first time, stable incorporation in the host genome and correct phenotypic expression of large DNA constructs mediated by ICSI.