Biology subjects

Saba-El-Leil, M. K.

Publications and source records attributed to Saba-El-Leil, M. K..

4 recordsLinked to original sources

bioRxiv2026

Off-the-shelf NIR-I fluorophores as ready-to-use NIR-II probes: screening and in vivo validation

Fluorescence imaging in the second near-infrared window (NIR-II, 950-1700 nm) offers reduced scattering, lower autofluorescence, and deeper tissue penetration than NIR-I imaging, but its adoption is limited by the need for custom-synthesized fluorophores. Here, we identify commercially available dyes that exhibit usable NIR-II emission. Eleven visible, far-red, and NIR-I fluorophores were screened under twelve acquisition configurations combining 670, 760, and 808 nm excitation with band-pass (950 nm, 1400 nm) or long-pass (1000 nm, 1250 nm) emission filters. Output varied markedly with fluorophore identity and excitation/emission configuration. Among hydrophobic dyes, DiR exhibited strong emission across almost all excitation and emission filters. Among hydrophilic dyes, strong NIR-II fluorescence was observed for IRDye 680RD (excitation at 670 nm), sulfo-cyanine 7 (excitation at 670 nm and 760 nm), and indocyanine green (excitation at 808 nm). DiR showed a linear concentration-response under 760 nm excitation with BP1400 detection. Upon encapsulation in PEGylated liposomes, strong NIR-II fluorescence was retained. In an in vivo study in mice, NIR-II resolved vasculature that NIR-I could not consistently delineate, and enabled pharmacokinetic analysis. Both windows returned similar ex vivo organ distributions. NIR-II imaging is therefore accessible using commercial off-the-shelf fluorophores, provided the dye is matched to the intended excitation/emission configuration.

bioengineering↗

bioRxiv2025

Transgenic Inducible MHC I Overexpression in Mouse Alveolar Type 2 Cells

The major histocompatibility complex class I (MHC I) is crucial in adaptive immunity, enabling CD8+ T cells to detect and eliminate infected and cancerous cells. Recent studies have uncovered significant variability in MHC I expression across tissues, challenging the traditional belief of uniform expression. Lung epithelial cells (LECs) express meager amounts of MHC I, which preserves the lung epithelium from excessive inflammation but renders it more susceptible to cancer and infection. Despite MHC I overexpression in various immunopathologies, its precise role in disease initiation or progression remains unclear due to the absence of suitable in vivo models for studying MHC I overexpression. This study introduces a novel mouse model with targeted surface MHC I upregulation. Leveraging a conditional Cre-lox system, we augmented Nlrc5 expression to specifically upregulate MHC I in alveolar type 2 (AT2) LECs, known for their low basal expression of MHC I and significant overexpression in disease. Our model demonstrated a rapid and sustained tenfold increase in MHC I surface expression persisting for up to a year without triggering pathology or inflammation. Comprehensive characterization and validation of this model indicated that MHC I overexpression does not serve as a primary initiator of respiratory diseases under steady-state conditions and shows a therapeutic window for increasing MHC I without significant damage to the lung epithelium. This adaptable model offers insights into the effects of tissue-specific MHC I regulation and presents new avenues for therapeutic development.

molecular biology↗

bioRxiv2023

OSGN-1 is a conserved flavin-containing monooxygenase required to stabilize the intercellular bridge in late cytokinesis

Cytokinesis is the last step of cell division and is regulated by the small GTPase RhoA. RhoA activity is required for all steps of cytokinesis, including prior to abscission when daughter cells are ultimately physically separated. Like germ cells in all animals, the C. elegans embryonic germline founder cell initiates cytokinesis but does not complete abscission, leaving a stable intercellular bridge between the two daughter cells. Here we identify and characterize C. elegans OSGN-1 as a novel cytokinetic regulator that promotes RhoA activity during late cytokinesis. Sequence analyses and biochemical reconstitutions reveal that OSGN-1 is a flavin-containing monooxygenase. Genetic analyses indicate that the monooxygenase activity of OSGN-1 is required to maintain active RhoA at the end of cytokinesis in the germline founder cell and to stabilize the intercellular bridge. Deletion of OSGIN1 in human cells results in an increase in binucleation as a result of cytokinetic furrow regression, and this phenotype can be rescued by expressing a catalytically-active form of C. elegans OSGN-1, indicating that OSGN-1 and OSGIN1 are functional orthologs. We propose that OSGN-1 and OSGIN1 are novel, conserved monooxygenase enzymes required to maintain RhoA activity at the intercellular bridge during late cytokinesis and thus promote its stability, enabling proper abscission in human cells and bridge stabilization in C. elegans germ cells.

cell biology↗

bioRxiv2018

Reevaluation of the Role of ERK3 in Perinatal Survival and Post-Natal Growth Using New Genetically-Engineered Mouse Models

The physiological functions of the atypical MAP kinase ERK3 remain poorly characterized. Previous analysis of mice with a targeted insertion of the lacZ reporter in the Mapk6 locus (Mapk6lacZ) showed that inactivation of ERK3 in Mapk6lacZ mice leads to perinatal lethality associated with intrauterine growth restriction, defective lung maturation, and neuromuscular anomalies. To further explore the role of ERK3 in physiology and disease, we generated novel mouse models expressing a catalytically-inactive (Mapk6KD) or conditional (Mapk6{Delta}) allele of ERK3. Surprisingly, we found that mice devoid of ERK3 kinase activity or expression survive the perinatal period without any observable lung or neuromuscular phenotype. ERK3 mutant mice reached adulthood, were fertile and showed no apparent health problem. However, analysis of growth curves revealed that ERK3 kinase activity is ncessary for optimal post-natal growth. To gain insight into the genetic basis underlying the discrepancy in phenotypes of different Mapk6 mutant mouse models, we analyzed the regulation of genes flanking the Mapk6 locus by quantitative PCR. We found that expression of several Mapk6 neighboring genes is deregulated in Mapk6lacZ mice, but not in Mapk6KD or Mapk6{Delta} mutant mice. Our genetic analysis suggests that off-target effects of the targeting construct on local gene expression are likely to be responsible for the perinatal lethality phenotype of Mapk6lacZ mutant mice.

developmental biology↗