Identifying the genetic basis of phenotypes arising during early development remains a central challenge in biology. The oocyte-to-embryo transition (OET) and early embryogenesis are uniquely dependent on maternally supplied factors and tightly regulated post-transcriptional programs, making the identification of maternal-effect genes particularly challenging. High-throughput sequencing technologies have fundamentally reshaped gene discovery during these stages, especially in genetically tractable vertebrate models such as zebrafish, where sequencing-based approaches enable rapid and largely unbiased identification of causal loci underlying maternal-effect phenotypes. Classical fine mapping, grounded in recombination and linkage analysis, has historically provided robust causal inference but is often labor-intensive and time-consuming. The advent of mapping-by-sequencing, which combines bulk segregant analysis with whole-genome sequencing, has transformed gene discovery by enabling efficient localization of causal variants associated with defects in oogenesis, egg activation, cleavage, and early patterning. Complementarily, RNA sequencing (RNA-seq) provides functional insight into disrupted maternal transcript programs, aberrant splicing, nonsense-mediated decay, and early zygotic responses. In some contexts, RNA-seq can also serve as a mapping substrate, although such approaches remain constrained by developmental stage and expression bias. In this review, we discuss how fine mapping, genome sequencing, and transcriptomic approaches can be strategically integrated to identify maternal-effect genes during the OET. Using zebrafish as a central model, we highlight key discoveries, methodological considerations, and emerging directions that extend phenotype-to-gene discovery toward mechanistic understanding of early development.
The autopod, the distal region of tetrapod limbs, represents a key evolutionary innovation requiring coordinated patterning, proliferation, and morphogenetic processes. While avian digit individualization has classically been described as driven almost exclusively by Programmed Cell Death (PCD) in the interdigital zone (IDZ), evidence from basal tetrapods indicates that differential growth between the digital zone (DZ) and IDZ originally mediated digit separation without apoptotic involvement. It remains unclear if this ancestral mechanism persists in amniotes or has been evolutionarily replaced by apoptosis. Here, we investigated growth dynamics in chicken (Gallus gallus) embryos by combining quantitative extension analyses, fluorescent DiI lineage tracing, and PH3-based proliferation assays. We demonstrate that differential growth is conserved in amniotes and arises through dynamic divergence in DZ and IDZ behaviour in chicken embryos. In chicken, although both regions expand comparably until HH32, IDZ extension declines markedly thereafter, while DZ outgrowth continues uninterrupted. DiI lineage tracing shows that the medial and proximal IDZ regions exhibit significantly greater extension at HH32 than at HH34, indicating a developmental decrease in growth that does not occur in the DZ, which maintains higher, stable extension rates across stages. Proliferation analyses align with these morphometric findings: the IDZ shows a sharp reduction in PH3-positive cells post-HH32, establishing a proliferative deficit relative to the DZ. Examination along the proximodistal axis revealed that the distal IDZ, influenced by the AER, shows the greatest proliferative activity, whereas medial and proximal regions contain fewer proliferative cells; this gradient is absent in the DZ, which displays relatively uniform proliferation. Together, these results indicate that avian digit separation is not governed solely by apoptosis but is initiated by an intrinsic decline in IDZ extension and cell-cycle activity. We propose that birds retain the ancestral differential growth mechanism, which works in concert with apoptosis to refine digit boundaries, bridging the evolutionary bridge between amphibian-like growth-driven individualization and amniote apoptotic refinement.
BACKGROUND:Although many genes have been implicated in spermatogenesis, their precise relationships to male fertility remain unclear. Here, we investigated the in vivo importance of the highly conserved, testis-enriched gene Samd7 as a potential regulator of murine spermatogenesis and fertility. METHODS:Samd7-/- mice were generated using CRISPR/Cas9. qPCR was used to assess Samd7 mRNA expression across mouse tissues. SAMD7 protein levels in testis were examined by Western blotting. Hematoxylin and eosin (H&E) staining of testis and epididymis was performed to evaluate spermatogenesis and sperm maturation. Immunofluorescence was used to characterize developmental stages of germ cells in the testis. Computer-assisted sperm analysis (CASA) was employed to measure sperm motility and related parameters. RESULTS:Samd7 expression was enriched in testis beginning at postnatal week 3. Compared with wild-type (Samd7+/+) littermates, Samd7-/- males showed no abnormalities in sperm content, testicular morphology, or fertility. Histology confirmed intact seminiferous tubules and normal testicular architecture in both Samd7+/+ and Samd7-/- mice. No differences were detected in sperm morphology or motility, including swimming velocity, in Samd7-/- mice. Testes and epididymides from Samd7-/- animals contained the expected spectrum of germ cells-from spermatogonia to mature spermatozoa-consistent with unimpaired spermatogenesis. CONCLUSIONS:These findings indicate that Samd7 is dispensable for murine spermatogenesis and male fertility under standard laboratory conditions.
The Wnt/β-catenin signaling pathway is a deeply conserved regulatory network that governs embryonic development, stem cell maintenance, and tissue homeostasis. Aberrant activation of the Wingless/Integrated protein (Wnt) signaling is a hallmark of numerous human diseases, most prominently in colorectal cancer, where it cooperates with additional oncogenic pathways to drive tumor initiation, progression, and therapeutic resistance (See Supplementary Table 1 for a list of the abbreviations used in this manuscript and their definitions.). Increasing evidence indicates that Wnt signaling does not function as an isolated linear cascade but rather as an integrative signaling hub that dynamically interfaces with major signaling pathways, including the RAS-RAF-MAPK and PI3K-AKT-mTOR pathways. Rat Sarcoma protein (RAS)- Rapidly Accelerated Fibrosarcoma protein (RAF)- Mitogen-Activated Protein Kinase (MAPK) and Phosphoinositide 3-Kinase (PI3K)- Ak strain transforming protein (AKT)- Mechanistic Target of Rapamycin (mTOR) pathways. These interactions occur at multiple molecular levels, encompassing shared kinases, transcriptional regulators, metabolic nodes, and cytoskeletal components, thereby coordinating proliferative, metabolic, and migratory programs. In this review, we synthesize current mechanistic and clinical insights into the crosstalk between Wnt signaling and the RAS-RAF-MAPK and PI3K-AKT-mTOR pathways, with particular emphasis on colorectal cancer. We discuss how these signaling networks converge to regulate β-catenin stability, transcriptional activity, cell adhesion, and metabolic reprogramming, thereby generating oncogenic phenotypes that cannot be explained by activation of individual pathways alone. To illustrate the evolutionary conservation and biological significance of these interactions, we integrate developmental paradigms from early Xenopus embryogenesis, where Wnt signaling governs zygotic genome activation, body axis formation, and the regulation of cell growth, protein stability, and biomass accumulation. Finally, we examine how an improved understanding of Wnt-centered signaling networks is informing emerging therapeutic strategies, including combinatorial pathway inhibition and nanoparticle-based drug delivery. Collectively, this review highlights Wnt signaling as a central integrator of developmental and oncogenic programs, providing a conceptual framework for understanding signaling network crosstalk and identifying new therapeutic opportunities in cancer.
BACKGROUND:Endometriosis is sustained by ectopic endometrial implants that remain proliferative and vascularized, making endocrine modulation a cornerstone of therapy. Estetrol (E4) an endogenous estrogen produced during pregnancy, with selective tissue activity, may modulate progesterone (P4) outputs in ectopic tissue and potentially shift lesion biology toward growth restraint without reinforcing vascular support. OBJECTIVE:To test whether E4 modifies P4 effects on lesion proliferation, apoptosis-related signaling, and angiogenic/endothelial activation in vivo. METHODS:Hormonally intact female mice bearing allografted endometriotic lesions received vehicle, E4 (3 mg/day), P4 (4.25 mg/day), or E4 + P4 once daily for 14 days. Lesions and eutopic endometrium were assessed by immunohistochemistry (Ki-67, cleaved caspase-3, BAX, VEGF, PECAM-1/CD31, Cyclin D1) with epithelial/stromal quantification, and endothelial angiogenic behavior was evaluated using a tube-formation assay. RESULTS:Lesions exhibited higher proliferative activity than eutopic endometrium. P4 reduced lesion proliferation, and the E4 + P4 combination produced the strongest growth restraint. Apoptosis-related markers increased under endocrine treatments, with the combined regimen showing robust activation. Notably, P4 enhanced angiogenesis-related readouts (VEGF and PECAM/CD31), whereas E4 + P4 prevented these increases and reduced endothelial tube formation, consistent with attenuated endothelial activation under the combined regimen. CONCLUSIONS:The E4-P4 combination supports a "balanced" endocrine profile-robust growth restraint without concurrent endothelial activation-thereby decoupling proliferation restraint from angiogenic activation.
