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RESUMEN Se reporta un paciente con síndrome de Frasier: nefropatía, disgenesia gonadal y daño renal progresivo y severo durante la infancia. El síndrome de Frasier es una entidad poco frecuente, que ocasiona enfermedad renal crónica terminal, por lo general, en adultos jóvenes, segunda o tercera décadas de la vida. La nefropatía se manifiesta con proteinuria, de inicio en la infancia, ocasionalmente con síndrome nefrótico, siendo la lesión histológica característica una glomeruloesclerosis focal y segmentaria, resistente al tratamiento con corticoides y/o inmunosupresores. La causa genética del síndrome de Frasier corresponde a mutaciones del gen supresor del tumor de Wilms o gen WT1 localizado en el brazo corto del cromosoma 11: Cr11p23.
ABSTRACT We report the case of a patient with Frasier syndrome: nephropathy, gonadal dysgenesis and progressive and severe kidney damage during childhood. Frasier syndrome is a rare disorder that causes end-stage chronic kidney disease, usually in young adults -second or third decades of life. Nephropathy presents with proteinuria, beginning during childhood, occasionally with nephrotic syndrome; its characteristic histological lesion is a focal segmental glomerulosclerosis, resistant to treatment with corticosteroids and/or immunosuppressants. Frasier syndrome is caused by mutations in the Wilms' tumor suppressor gene, or WT1 gene, located on the short arm of chromosome 11: Cr11p23.
RESUMEN
Triploids can play an important role in polyploid evolution. However, their frequent sterility is an obstacle for the origin and establishment of neotetraploids. Here we analyzed the microsporogenesis of triploids (x = 7) and the crossability among cytotypes of Turnera sidoides, aiming to test the impact of triploids on the origin and demographic establishment of tetraploids in natural populations. Triploids of T. sidoides exhibit irregular meiotic behavior. The high frequency of monovalents and of trivalents with non-convergent orientations results in unbalanced and/or non-viable male gametes. In spite of abnormalities in chromosome pairing and unbalanced chromosome segregation, triploids are not completely sterile and yielded up to 67% of viable pollen. Triploids that originated by the fusion of 2n × n gametes of the same taxon showed more regular meiotic behavior and higher fertility than triploids from the contact zone of diploids and tetraploids or triploids of hybrid origin. The reproductive isolation of T. sidoides cytotypes of different ploidy level is not strict and the 'triploid block' may be overcome occasionally. Triploids of T. sidoides produce diploid and triploid progeny suggesting that new generations of polyploids could originate from crosses between triploids or from backcrosses with diploids. The capability of T. sidoides to multiply asexually by rhizomes, would enhance the likelihood that a low frequency of neopolyploids can be originated and maintained in natural populations of T. sidoides.
