Identification of Genes Involved in the Differentiation of R7y and R7p Photoreceptor Cells in .

The R7 and R8 photoreceptor cells of the compound eye mediate color vision. Throughout the majority of the eye, these cells occur in two principal types of ommatidia. Approximately 35% of ommatidia are of the pale type and express in R7 cells and in R8 cells.

Malignant teratoid medulloepithelioma with retinoblastic and rhabdomyoblastic differentiation.

We describe an unusual case of malignant teratoid medulloepithelioma in which distinct populations of tumor cells with different immunohistochemical staining patterns existed within the same eye. A neuroblastic population exhibited atypical features of retinoblastoma, including organization into pseudo-Flexner-Wintersteiner and Homer-Wright rosettes. Other populations evolved in strikingly different patterns, with large fields of cells resembling astrocytes and intervening streams of spindle cells that suggested smooth muscle.

Benign hamartoma masquerading as a deep orbital hemangioma.

A 3-month-old infant with a digital hemangioma had relative proptosis of the left eye. Ultrasound, computed tomography, and magnetic resonance imaging showed a retro-orbital mass with features consistent with a capillary hemangioma. Despite the radiographic appearance, however, biopsy findings showed histologically benign tissues of a hamartomatous nature, inconsistent with a capillary hemangioma.

Two types of Drosophila R7 photoreceptor cells are arranged randomly: a model for stochastic cell-fate determination.

The R7 photoreceptor cells of the Drosophila retina are ultraviolet sensitive and are thought to mediate color discrimination and polarized light detection. In addition, there is growing evidence that the color sensitivity of the R8 cell within an individual ommatidium is regulated by a genetic switch that depends on the type of R7 cell adjacent to it. Here we examine the organization of the two major types of R7 cells by three different rigorous statistical methods and present evidence that they are arranged randomly and independently.

Expression of Drosophila rhodopsins during photoreceptor cell differentiation: insights into R7 and R8 cell subtype commitment.

The R7 and R8 photoreceptor cells of the Drosophila retina are thought to mediate color discrimination and polarized light detection. This is based on the patterned expression of different visual pigments, rhodopsins, in different photoreceptor cells. In this report, we examined the developmental timing of retinal patterning.