[The relevance of molecular biology studies in the genetic counselling of Argentine retinoblastoma families]. / Importancia de los estudios de biología molecular en el asesoramiento genético de familias argentinas con retinoblastoma.

OBJECTIVE: Evaluate the relevance of RB1 mutations detection in the genetic counselling of Argentine retinoblastoma families. METHODS: We included in this study 34 Argentine families with bilateral and unilateral Retinoblastoma (Rb). 130 DNA samples from leukocytes, tumors and chorionic villus were analyzed by indirect and direct molecular biology assays like Southern blot, segregation of polymorphisms BamHI, Rbi4, XbaI y Rb 1.20 (PCR-RFLP, PCR-STR), PCR-heteroduplex and sequencing of RB1 gene. RESULTS: Molecular biology analysis was informative in 18 out of 34 families studied (53%), 56% with bilateral and 44% with unilateral Rb. DNA tumor samples of 11 patients were available and could be studied by loss of heterozygosity (LOH) detection, that allowed us to identify the mutated RB1 allele in 9 (82%) patients. When tumor samples were not analized, the studies were informative only in 9 out of 23 patients (39%); we used direct mutation detection in 17 (41% informative) and indirect assays in 20 (60% informative) patients. CONCLUSIONS: The results prove the necessity to have DNA tumor, when the patient has been enucleated, and emphasize the importance of direct mutation detection in families with early sporadic Rb without tumor sample. The RB1 molecular biology contributed to the adequate genetic counselling of Argentine patients and relatives and their appropriate early treatment planning (Arch Soc Esp Oftalmol 2009; 84: 557-562).

Identification of RB1 germline mutations in Argentinian families with sporadic bilateral retinoblastoma.

Hereditary predisposition to retinoblastoma is caused by germline mutations in the RB1 gene. Most of these mutations occur de novo and differ from one patient to another. DNA samples from 10 families with a child presenting sporadic bilateral retinoblastoma have been analysed for the causative mutation. Using intragenic DNA polymorphisms we detected large deletions in two patients. Heteroduplex and DNA sequence analysis of PCR products from each exon and the promoter region showed small mutations in four patients: a C to T transition in exon 18; 1 bp and 2 bp deletion in exons 20 and 19 respectively; and a 4 bp insertion in exon 7. All these mutations are likely to result in premature termination of transcription. In one of these families, an unaffected carrier was detected. This emphasises the importance of detection of the causative mutation for predictive diagnosis in families with sporadic bilateral retinoblastoma.

Expression of c-myc and c-fos protooncogenes in the anterior pituitary gland of the rat. Effect of estrogen.

Thymidine incorporation into the DNA of the anterior pituitary gland is stimulated by estrogen. We studied the relationship between this effect and expression of the protooncogenes c-myc and c-fos. Within one hour after estrogen administration, the level of c-myc and c-fos mRNA increased in the anterior pituitary gland and remained high throughout the experimental period (16 to 22 hrs). Transcription of the prolactin gene, one of the targets of estrogen action, was stimulated at the same time intervals. There were no modifications in the growth hormone mRNA level. Thus, estrogen induced the expression of c-myc and c-fos in the anterior pituitary gland in an early period.

Expression of c-myc and c-fos oncogenes in different rat brain regions during postnatal development.

We have studied the expression of c-myc and c-fos proto-oncogenes in various areas of the central nervous system during postnatal development. c-myc mRNA levels increased during the first 5 days and then decreased over the next 15 days in all nervous regions studied. c-fos mRNA levels changed in a different way in four brain areas. While in cerebral cortex and cerebellum there was a sharp decrease during the first 10 days, in white matter and hypothalamus c-fos transcript levels remained high during the same period, decreasing at a later stage. Changes in oncogenes mRNA levels are related to various developmental events, such as neurite growth, myelination and cell proliferation. The dissimilar patterns of c-myc and c-fos expression suggests that they play different functions in CNS maturation. c-myc mRNA levels are temporally related to active neurite growth and to cell proliferation. Changes in c-fos mRNA correlate in time with early developmental processes and also with those occurring at later stages, such as myelination.