The Mouse Solitary Odorant Receptor Gene Promoters as Models for the Study of Odorant Receptor Gene Choice

Nanoodor Particles Deliver Drugs to Central Nervous System via Olfactory Pathway

Central nervous system (CNS) disorders confront significant challenges in drug delivery due to the blood-brain barrier (BBB). Inspired by the rapid and precise binding of odor molecules to olfactory receptors (ORs), this research uses thiolated HPMA to construct odor nanoparticles (nanoodors) capable of delivering drugs to the CNS via the olfacto-cerebral pathway to overcome the delivery obstruction. The nanoodor core is used to encapsulate agomelatine (AGO), a CNS-targeting antidepressant, and the encapsulation efficiency exceeded 80%. A series of thiol-presenting nanoscale structures with different surface densities of thiol groups are constructed, and the effectiveness positively correlated with the density of thiol groups on their surface. Notably, the nanoodors enable precise brain-targeted delivery, outperforming commercially available oral formulations in terms of drug accumulation in the brain and antidepressant effects. The study of the nanoodor transport and action mechanisms revealed that after binding to ORs, the nanoodors are rapidly delivered to the brain via the olfactory pathway. Nanoodors, the first design to deliver CNS drugs via the olfactory pathway by mimicking natural smells for the treatment of CNS disorders, are expected to achieve clinical transformation, benefiting human health.

A purely bioinformatic pipeline for the prediction of mammalian odorant receptor gene enhancers

BACKGROUND

In most mammals, a vast array of genes coding for chemosensory receptors mediates olfaction. Odorant receptor (OR) genes generally constitute the largest multifamily (> 1100 intact members in the mouse). From the whole pool, each olfactory neuron expresses a single OR allele following poorly characterized mechanisms termed OR gene choice. OR genes are found in genomic aggregations known as clusters. Nearby enhancers, named elements, are crucial regulators of OR gene choice. Despite their importance, searching for new elements is burdensome. Other chemosensory receptor genes responsible for smell adhere to expression modalities resembling OR gene choice, and are arranged in genomic clusters - often with chromosomal linkage to OR genes. Still, no elements are known for them.

RESULTS

Here we present an inexpensive framework aimed at predicting elements. We redefine cluster identity by focusing on multiple receptor gene families at once, and exemplify thirty - not necessarily OR-exclusive - novel candidate enhancers.

CONCLUSIONS

The pipeline we introduce could guide future in vivo work aimed at discovering/validating new elements. In addition, our study provides an updated and comprehensive classification of all genomic loci responsible for the transduction of olfactory signals in mammals.

Olfactory receptor OR2AT4 regulates human hair growth

Olfactory receptors are expressed by different cell types throughout the body and regulate physiological cell functions beyond olfaction. In particular, the olfactory receptor OR2AT4 has been shown to stimulate keratinocyte proliferation in the skin. Here, we show that the epithelium of human hair follicles, particularly the outer root sheath, expresses OR2AT4, and that specific stimulation of OR2AT4 by a synthetic sandalwood odorant (Sandalore^®) prolongs human hair growth ex vivo by decreasing apoptosis and increasing production of the anagen-prolonging growth factor IGF-1. In contrast, co-administration of the specific OR2AT4 antagonist Phenirat^® and silencing of OR2AT4 inhibit hair growth. Together, our study identifies that human hair follicles can engage in olfactory receptor-dependent chemosensation and require OR2AT4-mediated signaling to sustain their growth, suggesting that olfactory receptors may serve as a target in hair loss therapy.

Increasing evidence suggest that olfactory receptors can carry additional functions besides olfaction. Here, Chéret et al. show that stimulation of the olfactory receptor ORT2A4 by the odorant Sandalore^® stimulates growth of human scalp hair follicles ex vivo, suggesting the use of ORT2A4-targeting odorants as hair growth-promoting agents.

Regulatory Features for Odorant Receptor Genes in the Mouse Genome

The odorant receptor genes, seven transmembrane receptor genes constituting the vastest mammalian gene multifamily, are expressed monogenically and monoallelicaly in each sensory neuron in the olfactory epithelium. This characteristic, often referred to as the one neuron-one receptor rule, is driven by mostly uncharacterized molecular dynamics, generally named odorant receptor gene choice. Much attention has been paid by the scientific community to the identification of sequences regulating the expression of odorant receptor genes within their loci, where related genes are usually arranged in genomic clusters. A number of studies identified transcription factor binding sites on odorant receptor promoter sequences. Similar binding sites were also found on a number of enhancers that regulate in cis their transcription, but have been proposed to form interchromosomal networks. Odorant receptor gene choice seems to occur via the local removal of strongly repressive epigenetic markings, put in place during the maturation of the sensory neuron on each odorant receptor locus. Here we review the fast-changing state of art for the study of regulatory features for odorant receptor genes.