Olfactory Agenesis in Kallmann Syndrome (KS)

Anosmin1 Shuttles Fgf to Facilitate Its Diffusion, Increase Its Local Concentration, and Induce Sensory Organs

Growth factors induce and pattern sensory organs, but how their distribution is regulated by the extracellular matrix (ECM) is largely unclear. To address this question, we analyzed the diffusion behavior of Fgf10 molecules during sensory organ formation in the zebrafish posterior lateral line primordium. In this tissue, secreted Fgf10 induces organ formation at a distance from its source. We find that most Fgf10 molecules are highly diffusive and move rapidly through the ECM. We identify Anosmin1, which when mutated in humans causes Kallmann Syndrome, as an ECM protein that binds to Fgf10 and facilitates its diffusivity by increasing the pool of fast-moving Fgf10 molecules. In the absence of Anosmin1, Fgf10 levels are reduced and organ formation is impaired. Global overexpression of Anosmin1 slows the fast-moving Fgf10 molecules and results in Fgf10 dispersal. These results suggest that Anosmin1 liberates ECM-bound Fgf10 and shuttles it to increase its signaling range.

Olfactory bulb agenesis with normal sexual hormones

An 18-year-old Caucasian man presented with a lack of sense of surrounding smell. The problem was first noticed when a family member discussed the smell of the food, which he had no idea what it was. The patient had normal development and sexual function, no history of trauma, surgery, chemical exposure or infection. Physical examination revealed no significant abnormalities. Smell threshold test using phenyl-ethyl-alcohol revealed bilateral anosmia. MRI showed bilateral aplastic olfactory bulbs and tracts associated with absent cortical growth of the olfactory sulci and asymmetrical gyrus rectus. Circulating hormones including cortisol, growth hormone, insulin-like growth factor 1, adrenocorticotropic hormone, thyroid hormones, follicle-stimulating hormone, luteinizing hormone, prolactin and testosterone were within normal ranges. Doppler ultrasound showed normal testis with bilateral supratesticular varicoceles. Given the loss of warning smell sensation, counselling for daily living precautions especially those related to gas, fire and rotten food was given.