Faculty Bibliography

At the proximal part of mouse chromosome 17 there are three well-defined genes affecting the axis of the embryo and consequently tail length: Brachyury, Brachyury the second, and the t-complex tail interaction (T1, T2, and tct). The existence of T1 and tct in fact defines the classical "t-complex" that occupies approximately 40 cM of mouse chromosome 17. Their relationship to each other and various unlinked interacting genes has been enigmatic. The tint gene was the first of the latter to be identified. We report here its genetic mapping using a microsatellite scan together with outcrosses to Mus spretus and M. castaneous followed by a subsequent testcross to T, T1, and T2 mutants. Surprisingly, tint interacts with T2 but not with T1. The implications of our data suggest that T2 may be part of the T1 regulatory region through direct or indirect participation of tint.

Serum amyloid P (SAP) is a common component of human amyloid deposits and has been identified in atherosclerotic lesions. We investigated the extent of the colocalization of SAP with apolipoprotein A-I (apoA-I), apoB, apoC-II, and apoE in human coronary arteries and explored potential roles for SAP in these regions, specifically the effect of SAP on the rate of formation and macrophage recognition of amyloid fibrils composed of apoC-II. Analysis of 42 human arterial sections by immunohistochemistry and double label fluorescence microscopy demonstrated that SAP and apoA-I, apoB, apoC-II, and apoE were increased significantly in atherosclerotic lesions compared with nonatherosclerotic segments. SAP colocalized with all four apolipoproteins to a similar extent, whereas plaque macrophages were found to correlate most strongly with apoC-II and apoB. In vitro studies showed that SAP accelerated the formation of amyloid fibrils by purified apoC-II. Furthermore, SAP strongly inhibited the phagocytosis of apoC-II amyloid fibrils by primary macrophages and macrophage cell lines and blocked the resultant production of reactive oxygen species. The ability of SAP to accelerate apoC-II amyloid fibril formation and inhibit macrophage recognition of apoC-II fibrils suggests that SAP may modulate the inflammatory response to amyloid fibrils in atherosclerosis

Experiments involving beta-catenin loss- and gain-of-function in the mammary gland have decisively demonstrated the role of this protein in normal alveologenesis. However, the relationship between hormonal and beta-catenin signaling has not been investigated. In this study, we demonstrate that activated beta-catenin rescues alveologenesis in progesterone receptor (PR; Pgr)-null mice during pregnancy. Two distinct subsets of mammary cells respond to expression of DeltaN89beta-catenin. Cells at ductal tips are inherently beta-catenin-responsive and form alveoli in the absence of PR. However, PR activity confers beta-catenin responsiveness to progenitor cells along the lateral ductal borders in the virgin gland. Once activated by beta-catenin, responding cells switch on an alveolar differentiation program that is indistinguishable from that observed in pregnancy and is curtailed by PR signaling

The development of cerclage systems for fixation of greater trochanteric osteotomies has progressed from monofilament wires to multifilament cables to cable grip and cable plate systems. Cerclage wires and cables have various clinical indications, including fixation for fractures and for trochanteric osteotomy in hip arthroplasty. To achieve stable fixation and eventual union of the trochanteric osteotomy, the implant must counteract the destabilizing forces associated with pull of the peritrochanteric musculature. The material properties of cables and cable grip systems are superior to those of monofilament wires; however, potential complications with the use of cables include debris generation and third-body polyethylene wear. Nevertheless, the cable grip system provides the strongest fixation and results in lower rates of nonunion and trochanteric migration. Cable plate constructs show promise but require further clinical studies to validate their efficacy and safety

Desmosomes are cell-cell junctions responsible for maintaining the structural integrity of tissues by resisting shear forces. Defects result in diseases of mechanically challenged tissues such as skin and heart. The architectural design represents the key to understanding the strength and durability inherent to desmosomes. A number of different proteins contribute to this architecture, and X-ray crystallography has made considerable progress in defining the atomic structure of various isolated domains. Electron tomography has been used to determine the three-dimensional structure of intact desmosomes in situ. By combining information from X-ray crystallography, cell and molecular biology and electron tomography, it should ultimately be possible to deduce the specific protein interactions that define the mechanical properties of this important adhesive junction

Although TGFbeta is a potent inhibitor of proliferation, epithelia lacking the essential receptor (TbetaRII) for TGFbeta signaling display normal tissue homeostasis. By studying asymptomatic TbetaRII-deficient stratified epithelia, we show that tissue homeostasis is maintained by balancing hyperproliferation with elevated apoptosis. Moreover, rectal and genital epithelia, which are naturally proliferative, develop spontaneous squamous cell carcinomas with age when TbetaRII is absent. This progression is associated with a reduction in apoptosis and can be accelerated in phenotypically normal epidermis by oncogenic mutations in Ras. We show that TbetaRII deficiency leads to enhanced keratinocyte motility and integrin-FAK-Src signaling. Together, these mechanisms provide a molecular framework to account for many of the characteristics of TbetaRII-deficient invasive SQCCs

Rab11 and Rab6 guanosine triphosphatases are associated with membranes of the recycling endosomes (REs) and Golgi complex, respectively. Evidence indicates that they sequentially regulate a retrograde transport pathway between these two compartments, suggesting the existence of proteins that must co-ordinate their functions. Here, we report the characterization of two isoforms of a protein, Rab6-interacting protein 1 (R6IP1), originally identified as a Rab6-binding protein. R6IP1 also binds to Rab11A in its GTP-bound conformation. In interphase cells, R6IP1 is targeted to the Golgi in a Rab6-dependent manner but can associate with Rab11-positive compartments when the level of Rab11A is increased within the cells. Fluorescence resonance energy transfer analysis using fluorescence lifetime imaging shows that the overexpression of R6IP1 promotes an interaction between Rab11A and Rab6 in living cells. Accordingly, the REs marked by Rab11 and transferrin receptor are depleted from the cell periphery and accumulate in the pericentriolar area. However, endosomal and Golgi membranes do not appear to fuse with each other. We also show that R6IP1 function is required during metaphase and cytokinesis, two mitotic steps in which a role of Rab6 and Rab11 has been previously documented. We propose that R6IP1 may couple Rab6 and Rab11 function throughout the cell cycle.

Hypertrophic scars occur following cutaneous wounding and result in severe functional and esthetic defects. The pathophysiology of this process remains unknown. Here, we demonstrate for the first time that mechanical stress applied to a healing wound is sufficient to produce hypertrophic scars in mice. The resulting scars are histopathologically identical to human hypertrophic scars and persist for more than six months following a brief (one-week) period of augmented mechanical stress during the proliferative phase of wound healing. Resulting scars are structurally identical to human hypertrophic scars and showed dramatic increases in volume (20-fold) and cellular density (20-fold). The increased cellularity is accompanied by a four-fold decrease in cellular apoptosis and increased activation of the prosurvival marker Akt. To clarify the importance of apoptosis in hypertrophic scar formation, we examine the effects of mechanical loading on cutaneous wounds of animals with altered pathways of cellular apoptosis. In p53-null mice, with down-regulated cellular apoptosis, we observe significantly greater scar hypertrophy and cellular density. Conversely, scar hypertrophy and cellular density are significantly reduced in proapoptotic BclII-null mice. We conclude that mechanical loading early in the proliferative phase of wound healing produces hypertrophic scars by inhibiting cellular apoptosis through an Akt-dependent mechanism

Beta2 adrenergic receptors were identified in keratinocytes more than 30 years ago, but their function in the epidermis continues to be elucidated. Abnormalities in their expression, signaling pathway, or in the generation of endogenous catecholamine agonists by keratinocytes have been implicated in the pathogenesis of cutaneous diseases such as atopic dermatitis, vitiligo, and psoriasis. New studies also indicate that the beta2AR also modulates keratinocyte migration, and thus can function to regulate wound reepithelialization. This review focuses on the function of these receptors in keratinocytes and their contribution to cutaneous physiology and disease