Statins and downstream inhibitors of the isoprenylation pathway increase type 2 iodothyronine deiodinase activity.

The type 2 iodothyronine selenodeiodinase (D2) is a critical determinant of local thyroid signaling, converting T(4) to the active form T(3) at the cytoplasmic face of the endoplasmic reticulum, thus supplying the nucleus with T(3) without immediately affecting circulating thyroid hormone levels. Although inhibitors of the cholesterol synthesis/isoprenylation pathway, such as hydroxy-methyl-glutaryl-coenzyme A reductase inhibitors (statins) have been to shown to down-regulate selenoproteins via interruption of normal selenocysteine incorporation, little is known about the effect of statins on D2. Here, we report that statins and prenyl transferase inhibitors actually increase D2 activity in cells with endogenous D2 expression. Although we confirmed that lovastatin (LVS) decreases the activity of transiently expressed D2 in HEK-293 cells, the prenyl transferase inhibitors increase activity in this system as well. LVS treatment increases endogenous Dio2 mRNA in MSTO-211H cells but does not alter transiently expressed Dio2 mRNA in HEK-293 cells. The prenyl transferase inhibitors do not increase Dio2 mRNA in either system, indicating that a posttranscriptional mechanism must exist. Cotreatment with LVS or the prenyl transferase inhibitors with the proteasome inhibitor MG-132 did not lead to additive increases in D2 activity, indirectly implicating the ubiquitin-proteasomal system in the mechanism. Finally, C57BL/6J mice treated with LVS or farnesyl transferase inhibitor-277 for 24 h exhibited increased D2 activity in their brown adipose tissue. These data indicate that statins and downstream inhibitors of the isoprenylation pathway may increase thyroid signaling via stimulation of D2 activity.

Richer color experience in observers with multiple photopigment opsin genes.

Traditional color vision theory posits that three types of retinal photopigments transduce light into a trivariate neural color code, thereby explaining color-matching behaviors. This principle of trichromacy is in need of reexamination in view of molecular genetics results suggesting that a substantial percentage of women possess more than three classes of retinal photopigments. At issue is the question of whether four-photopigment retinas necessarily yield trichromatic color perception. In the present paper, we review results and theory underlying the accepted photoreceptor-based model of trichromacy. A review of the psychological literature shows that gender-linked differences in color perception warrant further investigation of retinal photopigment classes and color perception relations. We use genetic analyses to examine an important position in the gene sequence, and we empirically assess and compare the color perception of individuals possessing more than three retinal photopigment genes with those possessing fewer retinal photopigment genes. Women with four-photopigment genotypes are found to perceive significantly more chromatic appearances in comparison with either male or female trichromat controls. We provide a rationale for this previously undetected finding and discuss implications for theories of color perception and gender differences in color behavior.

A Nested Reverse Transcription-Polymerase Chain Reaction Assay to Detect BCR/abl.

Chronic myelogenous leukemia (CML), a clonal myeloproliferative disorder in adults, and some pediatric and adult acute lymphoblastic leukemias (ALLs) are characterized by the presence of a Philadelphia chromosome, t(9;22)(q34;q11) (1). In this chromosomal translocation, exons from a major breakpoint cluster region (M-bcr), located on chromosome 22q11, are joined to the c-abl proto-oncogene, located on chromosome 9q34. When this chromosomal translocation occurs in a hematopoietic stem cell, the resulting BCR/abl fusion protein has increased tyrosine kinase activity and a transforming capacity that is critical to the pathogenesis of these leukemic disorders.

Attitudes of physicians regarding receiving and storing patients' genetic testing results for cancer susceptibility.

In order to determine interest in and support for a genetic counseling program for heritable cancers, a four-item questionnaire was sent to 700 physicians in San Diego County likely to encounter patients with significant family histories of cancer. Included in the questionnaire was an item requesting information about physician attitudes and practices regarding their record keeping for patient results of genetic testing for cancer susceptibility. Ninety-two questionnaires were returned for a response rate of 13%. The low response rate introduces caution when interpreting the results, particularly if the physicians most interested in the topic were the most likely to respond. In this light, of note was the marked variability found in the attitudes of respondents regarding where the results of patients' genetic testing results should be placed in relation to the medical record. Whereas one group of physicians would place the testing results into the medical record, just as they would any laboratory test result, other physicians do not even want written notice of the results in order to maintain patient confidentiality. Another group acknowledges the sensitivity of the information, but prefers to store genetic testing results separately, as they would results of HIV testing or history of psychiatric treatment. Genetic testing for cancer susceptibility is associated with patient concerns regarding confidentiality of testing results and fears of the consequences of release of this information to insurance companies. While the small and possibly biased sample must be considered when interpreting the results, the lack of consistency among physicians about where to store genetic testing results in terms of the patient medical record underscores the need for both a consensus statement and legal protection for both patient and physician. Variability in physician practices suggests that the process of obtaining informed consent for genetic testing should include a discussion with the patient about how the confidentiality of test results will be maintained.

Detection of the factor VLeiden mutation. Development of a testing algorithm combining a coagulation assay and molecular diagnosis.

The Coagulation and Molecular Diagnostic laboratories at the University of Minnesota Medical School (Minneapolis) have collaborated to develop a diagnostic algorithm to identify all factor VLeiden mutation carriers without performing unnecessary and expensive genetic testing. The algorithm uses a coagulation assay for activated protein C resistance (APCR) to determine the need for genetic testing. We report the results of our experience validating this program. We compared the sensitivity, specificity, and positive and negative predictive values of two measures of APCR, the APCR ratio and the normalized ratio. We found that the normalized ratio was the more sensitive but less specific parameter to determine the need for genetic testing. By using the normalized ratio as the standard by which to refer patients to the Molecular Diagnostics Laboratory, all mutation carriers were identified. We found a large overlap in both measures of APCR between symptomatic patients with normal genotype and mutation carriers. Furthermore, we demonstrated that increased factor VIII levels with a normal genotype are associated with apparent APCR. In this article we also review other correlates of apparent APCR.

cAMP effects on myogenic gene expression in rhabdomyosarcoma cells.

Rhabdomyosarcoma is a tumor of skeletal muscle origin affecting children and young adults. Although relatively undifferentiated, cell lines derived from this tumor express myogenic regulatory factors and so may be useful models of abortive myogenic differentiation. In the present studies, we have determined the effect of increased intracellular cAMP on proliferation, morphologic differentiation, and expression of myogenic genes in the prototypic embryonal rhabdomyosarcoma cell line, RD. Whereas growth in dibutyryl cAMP (dbcAMP), forskolin, or butyrate led to morphologic differentiation, growth in dbcAMP inhibited proliferation, while growth in butyrate slowed but did not stop cell division. Expression of the genes for myogenin and myosin light chain was inhibited by dbcAMP, while butyrate decreased myogenin and increased myosin light chain transcription. MyoD and MRF4 expression was not altered under either condition and no myf5 expression was detected. We also determined the effects of dbcAMP and butyrate on total protein expression, as well as on a panel of muscle- and neural-specific proteins using functional assays, immunohistochemistry, and immunoprecipitation. The total protein levels of cells treated with either agent were double those of untreated cells. DbcAMP increased the activity of acetylcholinesterase (AChE) up to 10-fold compared to untreated cells, while butyrate had a substantially lesser effect. These increases were due to increased AChE protein synthesis and stability in dbcAMP treated cells, compared to butyrate or untreated cells. Finally, cells under all conditions expressed MAP2, a neural-specific microtubule associated protein. Together, these data suggest that intracellular cAMP levels modulate distinct subsets of the myogenic differentiation pathway in rhabdomyosarcoma cells. Moreover, they also indicate that RD cells are able to express markers of different cell lineages, which may help explain some of the paradoxical features of these tumors.

Clinical presentation of pedunculated, amelanotic melanoma: plantar aspect.

An historical review and case history of amelanotic malignant melanoma presenting as a pedunculated mass on the plantar aspect of the foot is discussed. The patient presented with a rapidly growing, cauliflower-like lesion on the plantar aspect of the left foot. Excisional biopsy revealed amelanotic malignancy. Subsequent surgical intervention was performed to effect a radical excision of local tissues with grafting and inguinal lymphadenectomy.