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Thomas Klein

Publications and source records attributed to Thomas Klein.

26 records · Page 2Linked to original sources
PubMed2003

The tumour suppressor gene l(2)giant discs is required to restrict the activity of Notch to the dorsoventral boundary during Drosophila wing development.

During the development of the Drosophila wing, the activity of the Notch signalling pathway is required to establish and maintain the organizing activity at the dorsoventral boundary (D/V boundary). At early stages, the activity of the pathway is restricted to a small stripe straddling the D/V boundary, and the establishment of this activity domain requires the secreted molecule fringe (fng). The activity domain will be established symmetrically at each side of the boundary of Fng-expressing and non-expressing cells. Here, I present evidence that the Drosophila tumour-suppressor gene lethal (2) gaint discs (lgd) is required to restrict the activity of Notch to the D/V boundary. In the absence of lgd function, the activity of Notch expands from its initial domain at the D/V boundary. This expansion requires the presence of at least one of the Notch ligands, which can activate Notch more efficiently in the mutants. The results further suggest that Lgd appears to act as a general repressor of Notch activity, because it also affects vein, eye, and bristle development.

Animals↗
PubMed2003

A Notch-independent function of Suppressor of Hairless during the development of the bristle sensory organ precursor cell of Drosophila.

Su(H)/CBF1 is a key component of the evolutionary conserved Notch signalling pathway. It is a transcription factor that acts as a repressor in the absence of the Notch signal. If Notch signalling is activated, it associates with the released intracellular domain of the Notch receptor and acts as an activator of transcription. During the development of the mechanosensory bristles of Drosophila, a selection process called lateral inhibition assures that only a few cells are selected out of a group to become sensory organ precursors (SOP). During this process, the SOP cell is thought to suppress the same fate in its surrounding neighbours via the activation of the Notch/Su(H) pathway in these cells. We show that, although Su(H) is required to prevent the SOP fate during lateral inhibition, it is also required to promote the further development of the SOP once it is selected. Importantly, in this situation Su(H) appears to act independently of the Notch signalling pathway. We find that loss of Su(H) function leads to an arrest of SOP development because of the loss of sens expression in the SOP. Our results suggest that Su(H) acts as a repressor that suppresses the activity of one or more negative regulator(s) of sens expression. We show that this repressor activity is encoded by one or several genes of the E(spl)-complex. Our results further suggest that the position of the SOP in a proneural cluster is determined by very precise positional cues, which render the SOP insensitive to Dl.

Animals↗
PubMed2003

Defective proventriculus is required for pattern formation along the proximodistal axis, cell proliferation and formation of veins in the Drosophila wing.

Many genes have been identified that are required for the establishment of the dorsoventral (DV) and anteroposterior (AP) axes of the Drosophila wing. By contrast, little is known about the genes and mechanisms that pattern the proximodistal (PD) axis. Vestigial (Vg) is instrumental in patterning this axis, but the genes that mediate its effects and the mechanisms that operate during PD patterning are not known. We show that the gene defective proventriculus (dve) is required for a region of the PD axis encompassing the distal region of the proximal wing (PW) and a small part of the adjacent wing pouch. Loss-of-function of dve results in the deletion of this region and, consequently, shortening of the PD axis. dve expression is activated by Vg in a non-autonomous manner, and is repressed at the DV boundary through the combined activity of Nubbin and Wg. Besides its role in the establishment of the distal part of the PW, dve is also required for the formation of the wing veins 2 and 5, and the proliferation of wing pouch cells, especially in regions anterior to wing vein 3 and posterior to wing vein 4. The study of the regulation of dve expression provides information about the strategies employed to subdivide and pattern the PD axis, and reveals the importance of vg during this process.

Animals↗
PubMed2002

kuzbanian is required cell autonomously during Notch signalling in the Drosophila wing.

The kuzbanian gene encodes a metalloprotease of the ADAM family that is involved in Notch signalling. However, its precise role is a matter of controversy. While original reports concluded that kuz is required on the receiving side of the Notch signalling pathway, a more recent report suggests that Kuz is required on the signal-emitting side for the generation of an active secreted form of the ligand Delta. In this scenario, kuz should act cell non-autonomously. A third possibility is that Kuz is required on the signal-emitting as well as the receiving side. Here I present the clonal analysis of kuz in Drosophila wing. The results show that Kuz acts on the receiving side of the pathway and is not required for Delta signalling. This further confirms the hypothesis that Kuz is required for the release of the intracellular domain of Notch that transduces the signal to the nucleus. The presented results complement recent data that indicate that Kuz can perform the S2 proteolytic cleavage of the Notch receptor that is required for its activation.

Animals↗
PubMed2002

[Social relationships, stress and mortality].

Empirically it has been demonstrated in many cases that social networks induce lower mortality rates. This article discusses various approaches to explain this phenomenon in consideration of the influence of stress. The empirical analysis refers to the complex interrelation between social networks, stress and mortality. In doing so, quantitative and qualitative aspects of social networks, different indicators of stress as well as the interaction effect of stress and social network is analyzed. Data derive from the German "MONICA Project" (MONICA=Monitoring of trends and determinants of cardiovascular diseases). The data comprise two cross-sectional surveys in 1984/85 and 1989/90 in the Augsburg area as well as a mortality follow-up in 1997/98. The study includes 7329 persons between the age of 25 and 74 years with German nationality. The empirical analyses confirm the findings that social relationships induce lower mortality rates. Yet, social relationships lead to lower mortality independent of stress and social strains.

Adult↗
PubMed2002

Reduced Th1 and enhanced Th2 immunity after immunization with Alzheimer's beta-amyloid(1-42).

It has been demonstrated that immunization of transgenic mouse models of Alzheimer's disease (AD) with amyloid-beta(1-42) peptide (Abeta(1-42)) results in prevention of Abeta plaque formation and amelioration of established plaques in the brain. As the response of the T lymphocyte helper (Th) arm of the immune response had not yet been investigated after Abeta immunization, we i.p. immunized C57BL/6 mice with Abeta(1-42), Abeta(1-40), or phosphate-buffered saline (PBS), and examined markers of Th1 and Th2 immune responses in spleen and in splenocytes from these mice. Spleens from Abeta(1-42)-immunized mice demonstrated decreased interleukin-12 receptor beta chain expression compared to mice immunized with Abeta(1-40) or PBS. Consistently, following stimulation with concanavalin A or anti-CD3 antibody, primary splenocytes from Abeta(1-42)-immunized mice demonstrated elevated secretion of interleukin-4 and interleukin-10, and decreased levels of interferon-gamma. To validate this Th1-->Th2 shift in a transgenic mouse model of AD, we immunized Tg APP(sw) mice (line 2576) with Abeta(1-42) and found decreased Th1 (interleukin-2 and interferon-gamma) and elevated Th2 (interleukin-4 and interleukin-10) cytokines in their stimulated primary splenocytes. Interferon-gamma was markedly reduced and interleukin-10 was increased in blood plasma from these mice, effects that were associated with dramatically mitigated Abeta deposition after Abeta(1-42) immunization. Taken together, these results show enhanced Th2 and down-regulated Th1 immunity following immune challenge with Abeta(1-42).

Alzheimer Disease↗
PubMed2002

Neurogenic hyperalgesia versus painful hypoalgesia: two distinct mechanisms of neuropathic pain.

Patients with sensory disturbances of painful and non-painful character show distinct changes in touch and/or pain sensitivity. The patterns of sensory changes were compared to those of human surrogate models of neuropathic pain to assess the underlying mechanisms. We investigated 30 consecutive in-patients with dysaesthesia of various origins (peripheral, spinal, and brainstem lesions) and 15 healthy subjects. Tactile thresholds were determined with calibrated von Frey hairs (1.1mm). Thresholds and stimulus-response functions for pricking pain were determined with a series of calibrated punctate mechanical stimulators (0.2mm). Allodynia was tested by light stroking with a brush, Q-tip, and cotton wisp. Perceptual wind-up was tested by trains of punctate stimuli at 0.2 or 1Hz. Intradermal injection of capsaicin (n=7) and A-fiber conduction blockade (n=8) served as human surrogate models for neurogenic hyperalgesia and partial nociceptive deafferentation, respectively. Patients without pain (18/30) showed a continuous distribution of threshold shifts in the dysaesthetic skin area with a low to moderate increase in pain threshold (by 1.52+/-0.45 log2 units). Patients with painful dysaesthesia presented as two separate groups (six patients each): one showing lowered pain thresholds (by -1.94+/-0.46 log2 units, hyperalgesia) and the other elevated pain thresholds (by 3.02+/-0.48 log2 units, hypoalgesia). The human surrogate model of neurogenic hyperalgesia revealed nearly identical leftward shifts in stimulus-response function for pricking pain as patients with spontaneous pain and hyperalgesia (by a factor of about 5 each). The sensory changes in the human surrogate model of deafferentation were similar to patients with hypoalgesia and spontaneous pain (rightward shift of the stimulus-response function with a decrease in slope). Perceptual wind-up did not differ between symptomatic and control areas. There was no exclusive association of any parameter obtained by quantitative sensory testing with a particular disease (of either peripheral or central origin). Our findings suggest that neuropathic pain is based on two distinct mechanisms: (I) central sensitization (neurogenic hyperalgesia; in patients with minor sensory impairment) and (II) partial nociceptive deafferentation (painful hypoalgesia; in patients with major sensory deficit). This distinction as previously postulated for postherpetic neuralgia, is obviously valid also for other conditions. Our findings emphasize the significance of a mechanism-based classification of neuropathic pain.

Adult↗