bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.01.06.698011

Lipid-mediated reinforcement of FGF/MAPK signaling enables robust otic placode specification

Peralta, S. R.·Maiorana, N.·Piacentino, M. L.
View original source ↗Export metadata ↓

Abstract

The formation of cranial placodes requires groups of ectodermal cells to interpret inductive signals in a robust and organized manner, yet how signaling responses are coordinated across a developing field remains incompletely understood. During otic placode specification, fibroblast growth factor (FGF) signaling must overcome intrinsic noise and rising inhibitory feedback to drive collective transcriptional responses, suggesting the existence of reinforcing regulatory events beyond ligand-receptor interactions and gene regulatory networks alone. Here we identify the secreted lipid-binding protein Apolipoprotein D (APOD) as an essential mediator of otic placode specification that links lipid-dependent regulation to FGF/MAPK signaling during early development. We find that APOD is strongly expressed in the forming otic placode, where it is necessary for otic specification and morphogenesis. Loss of APOD attenuates ERK1/2 activation, indicating impaired cellular responsiveness to FGF/MAPK signaling. Notably, FGF signaling induces APOD expression, establishing a positive feedback loop that reinforces signaling at the tissue level. These findings reveal lipid-mediated regulation of cell signaling as a critical mechanism enabling robust interpretation of developmental signals during sensory placode formation. More broadly, our work highlights lipid management as a key organizational principle by which embryonic tissues achieve coordinated responses to morphogenetic cues. HighlightsO_LIThe lipocalin Apolipoprotein D (APOD) is expressed transiently during early otic development C_LIO_LIAPOD is required for specification and morphogenesis of the otic placode C_LIO_LIAPOD functions upstream MAPK activation during otic specification C_LIO_LIFGF induces APOD expression to build a positive feedback loop C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=183 HEIGHT=200 SRC="FIGDIR/small/698011v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@12001ceorg.highwire.dtl.DTLVardef@56b35aorg.highwire.dtl.DTLVardef@1902eaorg.highwire.dtl.DTLVardef@e8817_HPS_FORMAT_FIGEXP M_FIG C_FIG

Explore related subjects

developmental biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Peralta, S. R., Maiorana, N., Piacentino, M. L.. 2026-01-07. Lipid-mediated reinforcement of FGF/MAPK signaling enables robust otic placode specification. https://doi.org/10.64898/2026.01.06.698011

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

A bicistronic Aldh1a3-P2A-TagBFP knock-in reporter mouse line for studying genitourinary tract development

Aldehyde dehydrogenase 1a3 (Aldh1a3) is an enzyme involved in retinoic acid synthesis with dynamic expression patterns during development, including in the urogenital system. Here, we generated a bicistronic Aldh1a3-P2A-TagBFP knock-in mouse using CRISPR/Cas9 genome editing, inserting TagBFP immediately upstream of the endogenous Aldh1a3 stop codon. Correct targeting was confirmed by Oxford Nanopore long-read sequencing, and heterozygous and homozygous mice were viable and fertile without overt morphological abnormalities. TagBFP fluorescence faithfully overlapped with endogenous Aldh1a3 immunoreactivity and reproduced established expression domains in the developing craniofacial region, intestine, kidney, and broader urogenital system. Extensive characterization of the urogenital system revealed dynamic, spatially restricted BFP reporter activity in Aldh1a3-expressing domains across several key structures, including the ureteric bud and collecting duct lineage, seminal vesicles, caput epididymis, and developing uterine horns. The Aldh1a3-P2A-TagBFP mouse provides a fluorescent resource for visualizing Aldh1a3 expression across development and in adult tissues, including for the characterization of Aldh1a3-expressing domains in the urogenital system. The relatively low fluorescence intensity of TagBFP should be considered when assessing low-level reporter expression.

developmental biology↗
bioRxiv2026

Translation of a small upstream open reading frame functions as a rheostat for the regulation of lin-41 by the Let-7 microRNA in Caenorhabditis elegans

MicroRNAs have been likened to the "dark matter" of eukaryotic genomes, reflecting their pervasive regulatory influence. MicroRNAs were first identified through genetic studies of developmental timing in the nematode Caenorhabditis elegans. Let-7 was the first microRNA recognized to be broadly conserved. The principal target of Let-7 in the developmental timing pathway is the TRIM-NHL RNA-binding protein LIN-41. During the L4 larval stage, Let-7 represses lin-41 translation by binding to two Let-7 complementary sites in the lin-41 3'UTR. Despite the importance of microRNA-based translational regulation, the underlying molecular mechanisms are incompletely understood. Through genetic analysis, we discovered an unrecognized feature of the mechanism by which Let-7 controls lin-41 translation. This mechanism requires a 5'-regulatory exon containing a seven-amino acid upstream open reading frame (uORF) and conserved sequence elements. Genome editing indicates that the specific uORF amino acid sequence itself is not important. Our data suggest that uORF translation and 5'UTR structure limit initiation at the downstream lin-41 start codon, enabling tight control by Let-7. Without this mechanism, the Let-7 microRNA is unable to properly regulate lin-41 to enable proper development.

developmental biology↗
bioRxiv2026

Ductal myofibroblasts reactivate contractile program to stabilize alveolar architecture during lung regeneration

The alveolar sac architecture is essential for efficient gas exchange and must be precisely maintained throughout life; however, how this delicate structure is preserved during adult regeneration remains poorly understood. Using a mouse pneumonectomy model, we found that Lgr6+ Hhip+ ductal myofibroblasts, a poorly characterized mesenchymal population, are indispensable for maintaining alveolar integrity during lung regrowth. Comprehensive characterization using single-cell transcriptomics, mouse genetics, and pharmacological assays demonstrated that these ductal myofibroblasts secrete myogenic factors, most notably CCN4, to reactivate a myogenic program that converts them into contractile PA-DMFs, thereby preserving alveolar architecture. Lineage-tracing further revealed that these ductal myofibroblasts originate from embryonic MCAM- SMA+ distal progenitors via subepithelial TGF-{beta} signaling, serving as a lifelong guardian of alveolar structural integrity. Notably, cross-species analysis identified an analogous population of LGR6+ fibromyocytes in human respiratory bronchioles. Together, these findings indicate ductal myofibroblasts as a developmentally programmed cell population that reactivate a contractile program to structurally support the regeneration of adult lungs.

developmental biology↗