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Molecular chastity - April 2008

Triggering off the making of a baby may seem a pretty straightforward process. Which it is, from a certain point of view. Yet, before any decisive action is undertaken by a woman and a man in order to unite their gametes, sperm – like ovules – have already been through a very complex series of developmental transformations. Such transformations ensure that only sperm and ovules of the same species get involved with one another, for example, or that once a couple of gametes has united no one else is allowed in. Properties of this sort are expressed on the molecular level both on the sperm’s and the ovule’s surface. One such molecule is a receptor known as zp3 found in mammals. Zp3 is expressed on the ovule’s surface and, though it is just one of many molecules, it is an essential one. Without it, sperm would not only be incapable of binding to the ovule’s membrane but they would also most probably miss their target altogether. (PDF version - 99k bytes)

Swiss-Prot cross references

Zona pellucida sperm-binding protein 3, Homo sapiens (Human): P21754
Zona pellucida sperm-binding protein 3, Mus musculus (Mouse): P10761
Zona pellucida sperm-binding protein 3, Rattus norvegicus (Rat): P97708

A dog's life - March 2008

Dogs were not meant to fit into a bag. Yet, some do. Consequently, instead of enjoying a healthy walk in the countryside they can go shopping with their owners. Convenience – both for humans and dogs – has trimmed down canine size in the past few hundred years. It is easier for dogs to be part of a household if they are medium-sized and more practical for humans to keep them if they are not too large. As such, natural selection coupled with selective breeding has supplied us with dogs ranging from barely twenty centimetres to giant samples which measure over one metre. And the stakes that a cross between a large poodle and a tiny Chihuahua will produce a medium-sized mongrel are high. So there must be a straightforward mechanism which is involved in their size. IGF1 – or insulin growth factor 1 – seems to be at the heart of such a mechanism. Indeed, scientists have discovered that small dogs all carry a certain variant of IGF1 while large dogs do not – or very few. This would suggest that the IGF1 variant has the power to reduce the size of a dog. (PDF version - 72k bytes)

Swiss-Prot cross references

Insulin-like growth factor 1, Canis familiaris (Dog): P33712

The hands to say it - February 2008

When I was a little girl, I thought that my left-handed classmates were special. I envied their difference. And I used to marvel at the way they crouched over their desk, embracing something invisible as they did their best to avoid smudging ink all over their sheet of paper. Left-handedness is special. But so is right-handedness. Humans are not the only animals to make use of their hands – or claws, or paws, or hooves - but they are the only ones who show a marked preference for either the left one, or the right one. If this is so, there must be a reason for it. And not only must there be a reason but it must translate a certain structure of our brain: an asymmetry somewhere. Indeed, our brain is divided into two hemispheres which are dedicated to processing different activities. One side looks after our dreams, while the other is far more down to earth. LRRTM1 is the first protein to have been discovered which seems to be directly involved in this brain asymmetry. Consequently, it influences the handedness of a human-being and, more astonishingly, may also predispose individuals to psychotic troubles such as schizophrenia. (PDF version - 65k bytes)

Swiss-Prot cross references

Leucine-rich repeat transmembrane neuronal protein 1, Homo sapiens (Human): Q96DN1

I'll have you for supper - January 2008

When there is nothing left to eat, we do not eat our parents or our children. We go down to the closest supermarket for food. Supermarkets, however, are not an option for bacteria. When they are short of nutrients, they are faced with a number of fates amongst which are sporulation, starvation or, for some, cannibalism. Indeed, Bacillus subtilis – a sporulating bacterium – has devised a way to feed on its sister cells in order to prolong its non-spore life. It does this by way of toxins which it produces itself and from which it must be protected to avoid committing suicide inadvertently… Needless to say, the molecular pathway is intricate and still obscure. However, hosts of proteins are being discovered, two of which are known as SkfA and SpdC whose actions result in B.subtilis sister cell lysis, from which the non-lysed cells will feed. (PDF version - 49k bytes)

Swiss-Prot cross references

Sporulation killing factor skfA, Bacillus subtilis : O31422
Killing factor sdpC, Bacillus subtilis : O34344
Immunity protein sdpI, Bacillus subtilis : O32241

Ear of stone - December 2007

The end of December is a time of year when many lose their balance. This, however, is usually due to the numbing of the senses by an exaggerated consumption of alcohol. There are many other ways of losing your balance, and one of them can be caused by an altered architecture of the inner ear. Besides bearing the intricate machinery which allows animals to perceive sound, the inner ear is also responsible for our sense of movement. Those who are stricken with sea-sickness know all too well what this means. Very small regions known as the saccule and the utricle detect both gravity and acceleration, two forces we spend our time dealing with. Deprived of the capacity to perceive them, the simple act of moving our head would prove to be an awesome experience. At the heart of this perception are small stones. And one protein, otopetrin 1, is proving to be essential for their formation. (PDF version - 79k bytes)

Swiss-Prot cross references

Otopetrin 1, Danio rerio (Zebrafish): Q7ZWK8
Otopetrin 1, Homo sapiens (Human): Q7RTM1
Otopetrin 1a, Mus musculus (Mouse): Q80VM9