The Left-Right Pitx2 Pathway Drives Organ-Specific Arterial and Lymphatic Development in the Intestine

SummaryThe dorsal mesentery (DM) is the major conduit for blood and lymphatic vessels in the gut. The mechanisms underlying their morphogenesis are challenging to study and remain unknown. Here we show that arteriogenesis in the DM begins during gut rotation and proceeds strictly on the left side, dependent on the Pitx2 target gene Cxcl12. Although competent Cxcr4-positive angioblasts are present on the right, they fail to form vessels and progressively emigrate. Surprisingly, gut lymphatics also initiate in the left DM and arise only after—and dependent on—arteriogenesis, implicating arteries as drivers of gut lymphangiogenesis. Our data begin to unravel the origin of two distinct vascular systems and demonstrate how early left-right molecular asymmetries are translated into organ-specific vascular patterns. We propose a dual origin of gut lymphangiogenesis in which prior arterial growth is required to initiate local lymphatics that only subsequently connect to the vascular system

Emergent Negative Differential Resistance with an Undisturbed Topological Surface State

Emergent properties in topological insulator heterostructures offer fresh insight not only to understand the system as a whole but also to design new approaches to device engineering at the nanoscale. Here we report the emergent phenomenon of negative differential resistance (NDR) on a topological insulator substrate. Starting with the spin-bearing cobalt fluorophthalocyanine molecule F16CoPc as the fundamental building block and the topological insulator (TI) Bi2Se3 as the host, using scanning tunneling spectroscopy (STS) we observe the emergence of NDR at the F16CoPc/Bi2Se3 interface at a specific negative bias. The topological surface state is also preserved in the process. Realizing NDR at the molecular scale presents a major advance toward designing ultrafast electron tunneling devices as well as high speed, low power, and compact nanoelectronic devices. The undisturbed topological surface state of Bi2Se3 offers added tunability for computer architectures that can be built concomitantly using the topological surface state and NDR

Absence of anaplastic lymphoma kinase-1 expression in inflammatory myofibroblastic tumors of the central nervous system: Does it signify a different nosologic entity from its systemic counterpart?

Background and Aim: Inflammatory myofibroblastic tumors (IMFTs) are uncommon neoplasms of the central nervous system (CNS) of intermediate grade biologic potential. Anaplastic lymphoma kinase (ALK-1), a diagnostic marker of anaplastic large cell lymphoma, is also expressed in a subset of IMFTs and appears to have prognostic significance. Though, few studies have evaluated expression of ALK-1 in IMFTs of the CNS. This retrospective study was undertaken to evaluate the expression of ALK-1 expression in IMFT of CNS by immunohistochemistry and correlate with the clinical, radiological and pathologic features. Materials and Methods: Five cases diagnosed as IMFT/inflammatory pseudotumour/plasma cell granuloma, diagnosed in CNS over 10 year period (1998-2007) were retrieved from the archives of Department of Neuropathology of a tertiary referralcenter. The clinical profile and imaging features were collected from the case records. Hematoxylin and eosin stained sections were reviewed with immunohistochemistry for smooth muscle actin (SMA), vimentin, desmin, ALK-1, p53, MIB-1, CD68, leukocyte common antigen, CD3, and CD20. Results: All five cases of IMFTs presented as dural-based space occupying or en-plaque lesions. Histologically, four cases had combined plasma cell granuloma-fibrous histiocytoma morphology, and one had fibrous histiocytoma-like morphology. Immunohistochemically, SMA was strongly positive in spindle cell component of the tumors confirming diagnosis. ALK-1 expression could not be detected by immunohistochemistry in any of the cases. Conclusion: Further studies analyzing ALK-1 gene mutation and rearrangements are required to determine pathogenetic role, if any, in CNS IMFTs

Distinct cellular roles for PDCD10 define a gut-brain axis in cerebral cavernous malformation

Cerebral cavernous malformation (CCM) is a genetic, cerebrovascular disease. Familial CCM is caused by genetic mutations in KRIT1, CCM2, or PDCD10 Disease onset is earlier and more severe in individuals with PDCD10 mutations. Recent studies have shown that lesions arise from excess mitogen-activated protein kinase kinase kinase 3 (MEKK3) signaling downstream of Toll-like receptor 4 (TLR4) stimulation by lipopolysaccharide derived from the gut microbiome. These findings suggest a gut-brain CCM disease axis but fail to define it or explain the poor prognosis of patients with PDCD10 mutations. Here, we demonstrate that the gut barrier is a primary determinant of CCM disease course, independent of microbiome configuration, that explains the increased severity of CCM disease associated with PDCD10 deficiency. Chemical disruption of the gut barrier with dextran sulfate sodium augments CCM formation in a mouse model, as does genetic loss of Pdcd10, but not Krit1, in gut epithelial cells. Loss of gut epithelial Pdcd10 results in disruption of the colonic mucosal barrier. Accordingly, loss of Mucin-2 or exposure to dietary emulsifiers that reduce the mucus barrier increases CCM burden analogous to loss of Pdcd10 in the gut epithelium. Last, we show that treatment with dexamethasone potently inhibits CCM formation in mice because of the combined effect of action at both brain endothelial cells and gut epithelial cells. These studies define a gut-brain disease axis in an experimental model of CCM in which a single gene is required for two critical components: gut epithelial function and brain endothelial signaling