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Many semiarid streams are threatened both by human demands and climatic effects (global warming), but little is known about their algal biodiversity and their conservation value, especially in Mediterranean areas. The aim of the present study was to evaluate annual changes in the structure and species richness of diatom communities in runs and pools of an oligohaline, semiarid stream in south-eastern Spain, and their relationship with nutrients and hydrology. The pool substrate was covered most of the time by a yellow-brown coat, mainly composed of diatoms and a few cyanophytes (Leptolyngbya). In the runs, cyanophytes were dominant (Rivularia) and diatoms occurred as epiphytes. The diversity of these diatom assemblages was high, particularly in the pools. Some species were present throughout the year, whereas others showed a bimodal growth pattern. Maximum biomasses were reached in summer in the pools and in autumn in the runs, when levels of phosphorus increased as a result of flooding. Species richness and diversity were correlated with hydrology and sulfate concentrations, whereas biomass (as chlorophyll a and ash-free dry weight) was associated with variations in temperature, conductivity and ammonium. These semiarid streams are refuges of biodiversity, representing habitats reliant on cycles of drought and floods, which should be considered in proposals for their conservation., Ministerio de Educación. Gobierno de España., Depto. de Biología Celular, Fac. de Ciencias Biológicas, TRUE, pub

Mammalian digit tip regeneration is linked to the presence of nail tissue, but a nail-explicit model is missing. Here, we report that nail-less double-ventral digits of dLARM1/2 mutants that lack limb-specific Lmx1b enhancers fail to regenerate. To separate the nail's effect from the lack of dorsoventral (DV) polarity, we also interrogate double-dorsal double-nail digits and show that they regenerate. Thus, DV polarity is not a prerequisite for regeneration, and the nail requirement is supported. Transcriptomic comparison between wild-type and non-regenerative dLARM1/2 mutant blastemas reveals differential upregulation of vascularization and connective tissue functional signatures in wild type versus upregulation of inflammation in the mutant. These results, together with the finding of Lmx1b expression in the postnatal dorsal dermis underneath the nail and uniformly in the regenerative blastema, open the possibility of additional Lmx1b roles in digit tip regeneration, in addition to the indirect effect of mediating the formation of the nail.

The developing limb is one of the main model systems to study biological pattern formation and evolutionary adaptation. Of particular importance is the establishment of dorso-ventral patterning (DV) as it gives rise to crucial DV asymmetries in the skeletal elements, nerves and vessels that enable the appendages to serve crucial functions such as stable locomotion on land and detailed manipulation.

n our role as medical educators and researchers, we support in the strongest manner possible the personal autonomy and self-determination of our students, patients, and colleagues. A fundamental value of the medical profession is for the patient to have personal autonomy in their healthcare decisions, including how they would like to be identified. It is, and will continue to be, an important priority to be taught and encouraged throughout healthcare education,1 and it begins in the anatomy laboratory with the proper and respectful treatment of body donors.2 Learning this value continues with respecting and accepting this same autonomy in fellow students, staff, faculty, and patients.

Complex signalling between the apical ectodermal ridge (AER - a thickening of the distal epithelium) and the mesoderm controls limb patterning along the proximo-distal axis (humerus to digits). However, the essential in vivo requirement for AER-Fgf signalling makes it difficult to understand the exact roles that it fulfils. To overcome this barrier, we developed an amenable ex vivo chick wing tissue explant system that faithfully replicates in vivo parameters. Using inhibition experiments and RNA-sequencing, we identify a transient role for Fgfs in triggering the distal patterning phase. Fgfs are then dispensable for the maintenance of an intrinsic mesodermal transcriptome, which controls proliferation/differentiation timing and the duration of patterning. We also uncover additional roles for Fgf signalling in maintaining AER-related gene expression and in suppressing myogenesis. We describe a simple logic for limb patterning duration, which is potentially applicable to other systems, including the main body axis.

The dorso-ventral (DV) organization of limb morphology is crucial for its function but little is known about how it is implemented during morphogenesis. Lmx1b is the key regulator of DV patterning as it is both necessary and sufficient to specify dorsal fates, but its regulation remains poorly known. Recently, we reported that Lmx1b is subject to a complex and autoregulatory mode of transcriptional regulation mediated by two limb-specific enhancers termed LARM1 and LARM2. Interestingly, these enhancers display anterior-posterior (AP) spatial modularity with LARM1 controlling Lmx1b expression in the anterior and LARM2 in the posterior half of the limb. To investigate the regulatory logic of the Lmx1b locus in higher detail, we have dissected the LARM1 enhancer and explored the functional contribution of two Lmx1b associated lncRNAs. The results confirm the presence of a functional repressor and underscore the AP positional specificity of the LARM sequences. Conjointly, the data suggests that Lmx1b transcription uses different regulatory elements in different positions probably reflecting the integration of the local transcriptional environment. Finally, since the double-ventral limbs of dLARM1/2 mutants fail to support locomotion, we hypothesized that the elaboration of the DV axis, possible driven by changes in the regulatory genome, had to accompany the fin transition towards appendages capable of lifting the body weight. In this direction, we have identified orthologs of the LARM sequences from chondrichthyans. All these sequences show activity in the pectoral fin in zebrafish reporter assays, revealing the deep roots of Lmx1b regulation.

[Background]: The development of the amniote limb has been an important model system to study patterning mechanisms and morphogenesis. For proper growth and patterning, it requires the interaction between the distal sub-apical mesenchyme and the apical ectodermal ridge (AER) that involve the separate implementation of coordinated and tissue-specific genetic programs., [Results]: Here, we produce and analyze the transcriptomes of both distal limb mesenchymal progenitors and the overlying ectodermal cells, following time-coursed dissections that cover from limb bud initiation to fully patterned limbs. The comparison of transcriptomes within each layer as well as between layers over time, allowed the identification of specific transcriptional signatures for each of the developmental stages. Special attention was given to the identification of genes whose transcription dynamics suggest a previously unnoticed role in the context of limb development and also to signaling pathways enriched between layers., [Conclusion]: We interpret the transcriptomic data in light of the known development pattern and we conclude that a major transcriptional transition occurs in distal limb buds between E9.5 and E10.5, coincident with the switch from an early phase continuation of the signature of trunk progenitors, related to the initial proximo distal specification, to a late intrinsic phase of development.

The regeneration of the digit tip is an exceptional model of multi-tissue regeneration in mammals, with remarkable potential to advance regenerative medicine. Digit tip regeneration positively correlates with the presence of the nail organ, most likely because of the environment of the nail stem cells, but the underlying mechanisms are still unclear. The fact that the nail is a dorsal structure links regeneration with dorso-ventral (DV) polarity. Here, to evaluate the nail function more directly, and to disentangle it from DV positional information, we tested the regenerative ability of double-ventral digits and double-dorsal digits resulting from the limb-specific loss of Lmx1b and of En1 expression, respectively. Our results indicate that DV polarity is not required for digit tip regeneration but that an excessive inflammatory response prevents regeneration in the absence of Lmx1b. The possible causes of the exacerbated inflammation in the absence of Lmx1b are discussed.

The dorso-ventral (DV) limb asymmetry is crucial for its function; however, little is known about how it is accomplished during morphogenesis. Lmx1b is the key regulator of DV patterning during limb development as it is both necessary and sufficient to specify dorsal fates, but its regulation remains poorly known. We recently demonstrated a complex autoregulatory mode of transcriptional Lmx1b regulation mediated by two limb-specific enhancers, LARM1 and LARM2. The deletion of both enhancers (dLARM1/2) reproduces the Lmx1b-null phenotype in the limb, while the removal of each enhancer produced a double ventral phenotype restricted to the posterior (dLARM1) or anterior (dLARM2) half of the limb. To investigate the regulatory logic of the Lmx1b locus in detail, we dissected the LARM1 element into its enhancer and silencer sequences and explored the functional contribution of the two Lmx1b-associated lncRNAs. The results confirm the presence of a functional repressor contained in LARM1 and underscore the positional specificity of the LARM sequences. The data suggests that Lmx1b transcription uses different regulatory elements in different positions probably reflecting the integration of the local transcriptional environment. Indeed, published ChIP-seq data showed the Gli3 and Hox13 are significantly enriched in the LARM sequences exposing their interaction with major limb regulators. Finally, considering that the double-ventral limbs of dLARM1/2 mutants fail to support locomotion, even to lift the body weight, we hypothesized that the elaboration of the DV asymmetry by modification of Lmx1b regulation, or its functional targets, had to accompany the fin to limb transition. We have identified orthologs of the LARMs in fishes and all of them show activity in the pectoral fin in zebrafish reporter essays, revealing the deep roots of Lmx1b regulation.

[Background]: The phalanges are the final skeletal elements to form in the vertebrate limb and their identity is regulated by signaling at the phalanx forming region (PFR) located at the tip of the developing digit ray. Here, we seek to explore the relationship between PFR activity and phalanx morphogenesis, which define the most distal limb skeletal elements, and signals associated with termination of limb outgrowth. [Results]: As Grem1 is extinguished in the distal chick limb mesoderm, the chondrogenesis marker Aggrecan is up-regulated in the metatarsals and phalanges. Fate mapping confirms that subridge mesoderm cells contribute to the metatarsal and phalanges when subridge Grem1 is down-regulated. Grem1 overexpression specifically blocks chick phalanx development by inhibiting PFR activity. PFR activity and digit development are also disrupted following overexpression of a Gli3 repressor, which results in Grem1 expression in the distal limb and downregulation of Bmpr1b. [Conclusions]: Based on expression and fate mapping studies, we propose that downregulation of Grem1 in the distal limb marks the transition from metatarsal to phalanx development. This suggests that downregulation of Grem1 in the distal limb mesoderm is necessary for phalanx development. Grem1 downregulation allows for full PFR activity and phalanx progenitor cell commitment to digit fate.

Mammalian limb regeneration is restricted to the distal third of terminal phalanges. Amputation of distal digit tips results in blastema formation and restoration of the missing part. This regenerative response has been linked to the presence of the nail, but digits without nails have not been evaluated. Here we interrogate the regenerative ability of the double-ventral digits of dLARM1/2 mutants, which lack dorsal nails due to the limb-specific absence of Lmx1b. We report that these nail-less digits fail to regenerate, supporting the nail requirement. Because the absence of dorso-ventral (DV) polarity could also impair regeneration, as reported in amphibians, we tested the double-dorsal double-nail digits of Del(27) mutants, which lack DV polarity due to the limb-restricted loss of En1. Since Del(27) digits did regenerate, we concluded that DV polarity is not required for digit tip regeneration. We documented continued dorsal expression of Lmx1b postnatally in the wild-type (WT) nail dermis. Moreover, there is uniform Lmx1b expression in WT regeneration-competent blastemas. Transcriptomic comparison between WT and dLARM1/2 mutant blastemas revealed differential up-regulation of gene signatures functionally associated with vascularization and connective tissue remodeling in WT mice. In contrast, the dLARM1/2 non-regenerative blastemas that lack Lmx1b expression show differential up-regulation of genes associated with inflammation and inflammatory processes. Conjointly, our data implicate a direct role for Lmx1b in digit tip regeneration by maintaining the nail dermis and promoting a competent blastema.

Regeneration in mammals is limited to the digit tips. The amputation of the distal tip of the terminal phalanx triggers the formation of an undifferentiated pool of progenitor cells called a blastema that will regenerate the multiple tissues required to restore the missing part. Digit tip regeneration is linked to the presence of the dorsal nail organ, as only amputations that conserve the nail matrix regenerate. However, the regenerative potential of digits without nails has not yet been tested. To evaluate nailless digits, we used dLARM1/2 mutants that develop digits with no nails due to the limb-specific loss of the dorsal limb determinant Lmx1b. We report that dLARM1/2 mutant digits are unable to regenerate, although they form a blastema. To test whether the lack of regeneration was due to the absence of dorso-ventral (DV) polarity, a concept suggested in amphibia, we evaluated Del(27) mutants that also lack DV polarity with nails on both dorsal and ventral aspects of distal phalanges due to ventral overexpression of Lmx1b. Unlike dLARM1/2 mutants, Del(27) mutant digits regenerated indicating that DV polarity is dispensable for regeneration. Interestingly, Lmx1b expression (which continues in the nail dermis postnatally) is detected uniformly in the blastema of WT, but not dLARM1/2 mutant mice. In addition, comparison of dLARM1/2 vs WT blastemal transcriptomes revealed that the mutants had defective pro regenerative processes such as vasculogenesis and extracellular matrix remodeling, while inflammatory pathways were exacerbated. Gene expressions typical of the nail dermis were also lost in dLARM1/2 digit tips, suggesting regulation by Lmx1b. Collectively, our data suggest a direct role for Lmx1b in digit tip regeneration maintaining the nail dermis and promoting a competent blastema.

The aim of the present study was to assess the presence of perfluoroalkyl acids (PFAAs), namely perfluoroalkane sulfonates and perfluoroalkyl carboxylic acids, in Spanish river basins in order to: identify potential spatiotemporal variations; evaluate the effectiveness of the measures implemented for the reduction/elimination of these pollutants; verify the fulfillment of the Environmental Quality Standards (EQSs) in the European Union. PFOS and PFOA were determined in 116 water samples from four sites in the Duero basin, the largest in the Iberian Peninsula, collected seasonally from 2013 to 2020. In addition, 30 fish sample composites from the sample banks of Duero, Tagus, Ebro, Eastern Cantabrian and Catalonian basins were analyzed for 15 PFAAs. Median PFOS and PFOA concentrations were 0.72 and 0.42 ng/L, ranging from values below the limit of quantification (LOQ) to 81 and 22 ng/L, respectively. During the studied period, 51% of water samples were above the EQS of 0.65 ng/L for PFOS. In the case of fish, the PFOS range was

Targeting early-stage lung cancer is vital to improve survival. However, the mechanisms and components of the early tumor suppressor response in lung cancer are not well understood. In this report, we study the role of Toll-like receptor 2 (TLR2), a regulator of oncogene-induced senescence, which is a key tumor suppressor response in premalignancy. Using human lung cancer samples and genetically engineered mouse models, we show that TLR2 is active early in lung tumorigenesis, where it correlates with improved survival and clinical regression. Mechanistically, TLR2 impairs early lung cancer progression via activation of cell intrinsic cell cycle arrest pathways and the proinflammatory senescence-associated secretory phenotype (SASP). The SASP regulates non-cell autonomous anti-tumor responses, such as immune surveillance of premalignant cells, and we observe impaired myeloid cell recruitment to lung tumors after Tlr2 loss. Last, we show that administration of a TLR2 agonist reduces lung tumor growth, highlighting TLR2 as a possible therapeutic target.