By Grant Jacobs 01/02/2016


With a little help from gene therapy and optogenetics, a blue light will get it up. Every now and then a research paper leaves me thinking, “well, that was unexpected”. Last week I encountered research describing an optogenetic erectile stimulator that allows blue-light to stimulate an erection.

Small molecules play a part in a lot of processes in our bodies. Changing high and low levels of these small molecules trigger biological processes.

Imagine you’re trying to change the balance of molecules inside a cell. Somehow you have to get a signal inside the cell.

Imagine now if that signal could be light. Now you have an external signal where you don’t have to give anything to the subject, just shine the light on them.

Optogenetics was nominated the field of the year in 2010. Like its name suggests, it’s light-induced genetics.

From pond muck to neurons

A great way to develop new biological tools is to borrow from ones already present in nature. Some types of pond algae track towards light using an ‘eye spot’, a little organelle within the algae.

Part of this organelle’s ‘trick’ is to respond to light by moving ions across a membrane, changing the charge potential (voltage) of the eye spot.

Ion channels are used throughout our bodies, including in our neurons (nerves).

Shepherding ions in or out of neurons changes their electric potential, causing the neuron to ‘fire’.

A lot of the work using optogenetics has been studying how particular neurons work, and using optogenetics to study animal behaviour.

The same light-triggering process can be used for other things too.

Light-induced erections

Nitrous oxide is best known when mixed with pure oxygen as laughing gas. Less well-known is its chemical cousin, nitric oxide. Nitric oxide is a molecule used to signal events without our bodies. It’s unusual in signalling molecules for being gaseous.

It’s part of the series of signals that cause an erection.

The blood-filled tissue that swells in a erection is the corpus cavernosum — the cavernous body of the penis. Nitric oxide activates guanylyl cyclase, producing cyclic guanosine monophosphate (cGMP). That prompts calcium ion channels to close, ultimately leading to the relaxation and influx of blood into the corpus cavernosum, and an erection.

(Biological pathways can be ridiculously elaborate; this is the simple version.)

The researchers added a version of Beggiatoa guanylate cyclase gene modified to be optimal for mammals* to rats. That’s the gene makes the protein activated by nitric oxide in the signals that create an erection.

The protein this gene makes responds to blue-light. When blue-light was shone on the rat penis, it prompted an erection – as their abstract says,

An erectile optogenetic stimulator (EROS), a synthetic designer guanylate cyclase producing a blue-light-inducible surge of the second messenger cyclic guanosine monophosphate (cGMP) in mammalian cells, enabled blue-light-dependent penile erection associated with occasional ejaculation after illumination of EROS-transfected corpus cavernosum in male rats.

Towards the future

Once the gene therapy is done, the patient doesn’t need to take anything – no pills required.

It also works by stimulating an erection rather than prolonging one. Products like Viagra work by reducing the breakdown of cGMP, prolonging the erection.

Another thing is that this by-passes the usual physiological stimulations that provoke an erection. In principle this could be useful for those with a variety of medical conditions. (Hypertension, heart and liver conditions, and so on.)

This would require further work and approval of this sort of gene therapy before it could be developed as a treatment.

More frivolously, I can also imagine it turning up in a situation comedy along the lines of ‘Who gets to control the remote?’

Footnotes

* The preview says the gene is human-codon optimised. This will work in mice too. The last bit of the preview I could read suggests they also tested it on human cells in vitro.

Caveat: This paper is from early last year, but it’s the first I’ve heard of it. I wrote much of this before realising that the paper is pay-walled, to my annoyance. I dislike working from pay-walled papers and even less working without the full manuscript – but also don’t like throwing away what I’d written. (Fortunately the first page of the preview covers a lot.)

The cover photo is from Wikimedia Commons, public domain. The image and description are taken from: Sema Nilgün Erdoǧan, Sexual life in Ottoman society, Dönence, 1996, isbn:9757054003, p.129-130, 18th century. “An unhappy wife is complaining to the Kaddi about her husband’s impotence. Her evidence is a zibik (dildo).”

Source:

A Synthetic Erectile Optogenetic Stimulator Enabling Blue-Light-Inducible Penile Erection.

Taeuk Kim, Marc Folcher, Marie Doaud-El Baba, Prof. Martin Fussenegger

Angewandte Chemie 54(20)5933–5938 May 11, 2015

DOI: 10.1002/anie.201412204

Abstract:

Precise spatiotemporal control of physiological processes by optogenetic devices inspired by synthetic biology may provide novel treatment opportunities for gene- and cell-based therapies. An erectile optogenetic stimulator (EROS), a synthetic designer guanylate cyclase producing a blue-light-inducible surge of the second messenger cyclic guanosine monophosphate (cGMP) in mammalian cells, enabled blue-light-dependent penile erection associated with occasional ejaculation after illumination of EROS-transfected corpus cavernosum in male rats. Photostimulated short-circuiting of complex psychological, neural, vascular, and endocrine factors to stimulate penile erection in the absence of sexual arousal may foster novel advances in the treatment of erectile dysfunction.

Other articles on Code for life:

Aww, crap.

The inheritance of face recognition (should you blame your parents if you can’t recognise faces?)

Monday potpourri: maps, malaria in the USA, cholera in Dunedin and vaccines

Haemophilia – towards a cure using genetic engineering


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