-
[show abstract]
[hide abstract]
ABSTRACT: Morphogens orchestrate tissue patterning in a concentration-dependent fashion during vertebrate embryogenesis, yet little is known of how positional information provided by such signals is translated into discrete transcriptional outputs. Here we have identified and characterized cis-regulatory modules (CRMs) of genes operating downstream of graded Shh signaling and bifunctional Gli proteins in neural patterning. Unexpectedly, we find that Gli activators have a noninstructive role in long-range patterning and cooperate with SoxB1 proteins to facilitate a largely concentration-independent mode of gene activation. Instead, the opposing Gli-repressor gradient is interpreted at transcriptional levels, and, together with CRM-specific repressive input of homeodomain proteins, comprises a repressive network that translates graded Shh signaling into regional gene expression patterns. Moreover, local and long-range interpretation of Shh signaling differs with respect to CRM context sensitivity and Gli-activator dependence, and we propose that these differences provide insight into how morphogen function may have mechanistically evolved from an initially binary inductive event.
Developmental cell 11/2012; 23(5):1006-19. · 13.36 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The severe disorders associated with a loss or dysfunction of midbrain dopamine neurons (DNs) have intensified research aimed at deciphering developmental programs controlling midbrain development. The homeodomain proteins Lmx1a and Lmx1b are important for the specification of DNs during embryogenesis, but it is unclear to what degree they may mediate redundant or specific functions. Here, we provide evidence showing that DN progenitors in the ventral midbrain can be subdivided into molecularly distinct medial and lateral domains, and these subgroups show different sensitivity to the loss of Lmx1a and Lmx1b. Lmx1a is specifically required for converting non-neuronal floor-plate cells into neuronal DN progenitors, a process that involves the establishment of Notch signaling in ventral midline cells. On the other hand, lateral DN progenitors that do not appear to originate from the floor plate are selectively ablated in Lmx1b mutants. In addition, we also reveal an unanticipated role for Lmx1b in regulating Phox2a expression and the sequential specification of ocular motor neurons (OMNs) and red nucleus neurons (RNNs) from progenitors located lateral to DNs in the midbrain. Our data therefore establish that Lmx1b influences the differentiation of multiple neuronal subtypes in the ventral midbrain, whereas Lmx1a appears to be exclusively devoted to the differentiation of the DN lineage.
Development 08/2011; 138(16):3399-408. · 6.60 Impact Factor
-
Lia Panman,
Elisabet Andersson, Zhanna Alekseenko,
Eva Hedlund,
Nigel Kee,
Jamie Mong,
Christopher W Uhde,
Qiaolin Deng,
Rickard Sandberg,
Lawrence W Stanton,
Johan Ericson,
Thomas Perlmann
[show abstract]
[hide abstract]
ABSTRACT: The generation of specific types of neurons from stem cells offers important opportunities in regenerative medicine. However, future applications and proper verification of cell identities will require stringent ways to generate homogeneous neuronal cultures. Here we show that transcription factors like Lmx1a, Phox2b, Nkx2.2, and Olig2 can induce desired neuronal lineages from most expressing neural progenitor cells by a mechanism resembling developmental binary cell-fate switching. Such efficient selection of cell fate resulted in remarkable cellular enrichment that enabled global gene-expression validation of generated neurons and identification of previously unrecognized features in the studied cell lineages. Several sources of stem cells have a limited competence to differentiate into specific neuronal cell types; e.g., dopamine neurons. However, we show that the combination of factors that normally promote either regional or dedicated neuronal specification can overcome limitations in cellular competence and also promote efficient reprogramming in more remote neural contexts, including human neural progenitor cells.
Cell stem cell 06/2011; 8(6):663-75. · 23.56 Impact Factor
-
Stina Friling,
Elisabet Andersson,
Lachlan H Thompson,
Marie E Jönsson,
Josephine B Hebsgaard,
Evanthia Nanou, Zhanna Alekseenko,
Ulrika Marklund,
Susanna Kjellander,
Nikolaos Volakakis,
Outi Hovatta,
Abdeljabbar El Manira,
Anders Björklund,
Thomas Perlmann,
Johan Ericson
[show abstract]
[hide abstract]
ABSTRACT: Signaling factors involved in CNS development have been used to control the differentiation of embryonic stem cells (ESCs) into mesencephalic dopamine (mesDA) neurons, but tend to generate a limited yield of desired cell type. Here we show that forced expression of Lmx1a, a transcription factor functioning as a determinant of mesDA neurons during embryogenesis, effectively can promote the generation of mesDA neurons from mouse and human ESCs. Under permissive culture conditions, 75%-95% of mouse ESC-derived neurons express molecular and physiological properties characteristic of bona fide mesDA neurons. Similar to primary mesDA neurons, these cells integrate and innervate the striatum of 6-hydroxy dopamine lesioned neonatal rats. Thus, the enriched generation of functional mesDA neurons by forced expression of Lmx1a may be of future importance in cell replacement therapy of Parkinson disease.
Proceedings of the National Academy of Sciences 05/2009; 106(18):7613-8. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The prospect of using cell replacement therapies has raised the key issue of whether elucidation of developmental pathways can facilitate the generation of therapeutically important cell types from stem cells. Here we show that the homeodomain proteins Lmx1a and Msx1 function as determinants of midbrain dopamine neurons, cells that degenerate in patients with Parkinson's disease. Lmx1a is sufficient and required to trigger dopamine cell differentiation. An early activity of Lmx1a is to induce the expression of Msx1, which complements Lmx1a by inducing the proneural protein Ngn2 and neuronal differentiation. Importantly, expression of Lmx1a in embryonic stem cells results in a robust generation of dopamine neurons with a "correct" midbrain identity. These data establish that Lmx1a and Msx1 are critical intrinsic dopamine-neuron determinants in vivo and suggest that they may be essential tools in cell replacement strategies in Parkinson's disease.
Cell 02/2006; 124(2):393-405. · 32.40 Impact Factor
