Posts Tagged ‘Embryogenesis’

A baby lacking a brain

// December 17th, 2009 // Comments Off on A baby lacking a brain // Sex and Reproduction

I’ve been struggling with writing this. After doing a little research into it I found some pictures that just… when I get concerned about something I tend to obsessively check facebook and twitter, like I’m looking for someone to connect to and I’m too freaked to reach out.

I came across a beautifully written post that talked about a birth defect that I’ve read about before, in which babies are born lacking a significant portion of the brain. It’s called Holoprosencephaly or Anencephaly, depending some factors I can’t research into at the moment. The first one can come in a range of severeties, from mild midline defects (such as only having one middle tooth, or eyes that are too close together) to severe midline defects (such as only having one eye, or a tube-shaped nose called a proboscis) to death. Some studies suggest that it may be quite common, but because it often ends with spontaneous abortion you wouldn’t really know (it seems they say that about a number of defects… Trisomy comes to mind.) About 1 in 10,000 live births will have a form of holopresencephaly.

There’s nothing more I want to say about this, really. It takes a lot to move this salty sea dog to tears, but this incredibly beautiful and sad true story told by a medical student did. It is called “Bittersweet”, but be warned, it’s emotional. You can read more about holopresencephaly from the same writer. Now I’m going to check facebook and twitter again.

Cheap date, grim reaper and swiss cheese – the world’s coolest gene names

// December 3rd, 2009 // 2 Comments » // Jibber Jabber, Just for Fun, Sex and Reproduction

0507-hello_my_name_is1

I studied biochemistry at University, and I remember spending hours copying pathways, reading and rereading textbooks, then summarising, checking, drawing, testing, making mnemonics, in short EVERYTHING I could do to help me memorise things. There is a lot to remember in biochemistry, and a lot of words which don’t mean much that have to go in the right place. JAK activates JEK activates MEK which activates an enzyme which travels to the nucleus and binds to blah which attaches to blah region of the DNA and has the effect of increasing glucose absorption. Or something. Frankly I can’t remember anymore, and I’m damn glad I don’t have to try.

Meaningless acronyms are an annoying part of science, and of any job really. At work I talk about getting a tvc cadded, matching the key to the clapper and ingesting it – to anyone who hasn’t done TV advertising this is complete jibberish. Biochemistry is really no different – if you don’t know much about it, it’s because no one has explained it to you properly using normal words.

This post is not about normal words. Screw normal words! This is about the awesome, the spectacular, the creative and the downright weird.

These are some of the coolest names I have come across for proteins and genes, and a lot of them are found in the fruit fly Drosophila. Drosophila is the white lab rat of developmental science, it’s always the guinea pig because it reproduces REALLY fast, and creates multiple offspring in a single frenzy. Some other species (including humans) also get a mention in this list.

Tinman – Drosophila with a mutation to tinman develop with no heart.
Maggie – a mutation causes arrested development, in the Simpsons Maggie never ages.
Cheap Date – mutation causes Drosophila to be extra sensitive to alcohol. Another gene called Lush does the same thing.
Cleopatra – Cleopatra was killed by an asp, and interaction of mutant Cleopatra protein with the Asp protein is lethal.
Ken and Barbie – mutants (both male and female) lack external genitals.
Swiss Cheese – mutants have holes in their brain.
Grim Reaper – two separate genes, together they cause cell death.

For those biblically minded of us, there is Lot – mutants have more salt than usual, or Sarah – mutants are almost sterile, or Methuselah – mutants live extra long. Prefer Greek Myths? How about Ariadne, who showed Theseus how to get through the Minotaurs Labyrinth – in Drosophila, Ariadne mutants stop the axons of nerve cells finding their targets. Love Shakespeare (who doesn’t?), take Hamlet – which affects development of cells descended from IIB cells – “to be or not to be.”

Sometimes the names help us remember how things link together, take these names from Arabidopsis thaliana, a small flowering plant that’s like the Drosophila of plant genetics. Superman mutants have extra stamens in their flowers, while the Clark Kent is a milder version of the mutation, and Kryptonite suppresses the function of Superman.

Zebrafish have some neat ones too – including one-eyed pinhead, cyclops and squint – all important in the development of an embryo.

How about in humans? Well yesterday I talked about a spiky little protein called Sonic Hedgehog, which was originally found in, you guessed it, Drosophila, but which plays an important role in embryo development in humans. There’s not a huge number of genes with cool names in humans, and there’s a good reason for that. Imagine you had a child who was very sick and you met with the doctor, who looked at you seriously and said “I’m sorry, it’s genetic. Your son has a mutation in the Sonic Hedgehog gene.” There are a couple of others, like Tigger which is a segment of DNA which hops around into different locations

Those are my faves, but there’s plenty more out there. These are samples from My Favourite Gene Names and Gene Names by Organism, and I know there’s others that didn’t make the list. FlyNome has a searchable database of heaps of Drosophila genes and the story behind them. It’s almost worth getting into Drosophila research just for the cool names, plus imagine if you found a new gene and got to name it yourself… oh the possibilities…

Baby teeth, where your cheesy grin comes from

// December 2nd, 2009 // Comments Off on Baby teeth, where your cheesy grin comes from // How Things Work, Science at Home

brushing teeth

Look into the screen and smile. Ever wondered where those teeth o’ yours came from? Whence did they sprout, sharp, strong and shiny from yon glistening gums? And why did ye have baby teeth which grew and survived a good ten years before being mercilessly replaced?

I am fortunate to still have all my teeth, I blessing I attribute to my penchant for Mojitos. Being full of lime juice, they protects me from the dreaded scurvy which has taken the teeth of many a mighty pirate.

Baby teeth start forming before there is a baby, back when you are just a little itty bitty embryo, about 6 weeks after conception. Their growth is under the control of a protein called Sonic Hedgehog, one of three proteins in the Hedgehog family, the other two being Desert Hedgehog and Indian Hedgehog. The hedgehogs are involved in a lot of minor jobs when the embryo is developing, like making limbs grow in the right place.

Sonic Hedgehog was originally discovered in our favourite developmental genetics model – the Drosophila the fruit fly. Proteins in Drosophila almost always have kick-ass names, in fact an inhibitor of this pathway is called Robotnikinin, after Sonic’s nemesis Dr. Robotnik. This time we kept the cool protein name for the same protein in humans, which makes a welcome change from the usual names like APK, JAK and JEK *snore*.

The road to teeth begins with a tooth bud, a group of cells that want to be a tooth when they grow up. They organise themselves into three groups, enamel (the stuff on the outside which protects the tooth from wear and tear), dental papilla (which forms dentin, the bulk of the tooth) and dental follicle (which becomes the important stuff that attaches the tooth to your mouth). The baby teeth form first, and the adult teeth start forming around 20 weeks after conception. You’ll have 20 baby teeth and 32 adult teeth during your lifetime.

Tooth diagram

Why have baby teeth at all? Well, a baby doesn’t have a very big mouth, and 32 adult size teeth might look a tad ridiculous. The baby teeth also pave the way for adult teeth, acting as a guide for where the next lot should erupt from. Plus we can’t overlook the fact that the tooth fairy needs ammunition for her secret underground tooth-driven missile factory. The $20 or so I got over the years is enough reason for me. If only we could lose more during those years, like the Southpark gang do in The Tooth Fairy Tats, I wouldn’t have to constantly hunt for treasure.

Sharks have about three rows of teeth and as soon as they lose one (which they do constantly), another one can slip in and take it’s place while a new one grows up behind it. An endless supply of teeth! The best we do is the four wisdom teeth which kick in when we’re 20 or so, which was pretty old back in cavemen days and would have been most excellent replacements for teeth lost in battle with zombies or gnawed away on dinosaur bones. Nowadays, with both zombies and dino’s in short supply, we mostly rip out our wisdom teeth and spend a week on heavy pain medication. I remember those days through a dim fog of jelly, yogurt and Boston Legal. Aye, those were the days.

Actually that sucked. I woke up from the anaesthetic like I’d been punched in the face, and had balls of cotton in my mouth. I groggily asked the nurse if I could take out the cotton, and she tsked and took it away, but soon my mouth was full of blood and I had to ask for more cotton and she tsked even MORE! And it felt so weird, and the stitches made me feel like a poorly made doll, and I looked mostly like a chipmunk with bruised cheeks. It was not an attractive time. Not even the jelly made it worthwhile, so no more losing teeth for me. Pass me that Mojito!

When shark embryos get hungry an unborn sibling makes a tasty treat

// November 25th, 2009 // 4 Comments » // Sex and Reproduction, The Realm of Bizzare

Next time you run out of food in the fridge ask yourself this, would you eat a human? If you were in a plane crash in the middle of a desert, would you eat the person who sat next to you, or would you brave the supply of frozen muffins and green omelettes they serve as sky “food”? For your own survival, would you kill and eat your brother or sister?

Some species of shark do indeed feast on their siblings, not just out in the deep blue sea, but while still inside the uterus. Now that’s taking sibling rivalry to a whole new level.

Sharks reproduce in three ways – they either species lay eggs and leave them to hatch, or they lay eggs and let them hatch in the uterus and then give birth to them, or they have a live births. Feeding a growing embryo while it develops in the womb is quite a challenge for sharks, but they have some crazy methods to do it.

Some species, such as the lemon shark, turn their yolk sac into a placenta by attaching it to the wall of the uterus. Salmon shark embryos eat a stream of unfertilized eggs while their in the womb, providing them with plenty of nummy nutrients. Nurse sharks and sand tiger sharks, at the tender age of not even born yet, swim about and eat their siblings. From the 20 or so pups that start life, only two remain – natural selection starting early *they grow up so fast*

This video from the documentary Animals in the Womb has incredible footage of sand tiger shark embryonic cannibalism.

Why do two pups survive, and not just one? Sharks have two wombs, at least, their uterus has two separate branches that keeps the two pups apart. Apparently having their own room helps curb their aggression, who’d have thought?

Claymation Biology!

// October 16th, 2009 // Comments Off on Claymation Biology! // How Things Work, Science Communication, Sex and Reproduction

Science and animation belong together (wink). Animation is awesome sauce on science noms – “it makes science fun!” And how good is claymation? LOVE IT! It takes so long though, I don’t know how people have the patience.

Check out this video by Creature Cast, a clay-tastic introduction on what germ cells are and where they come from. Germ cells are the ones that become eggs and sperm, by the way.

CreatureCast Episode 2 from Casey Dunn on Vimeo.

The video raises interesting questions on developmental biology, and how cells which have the same genetic code end up being very different in function. It’s because of the way the genes are READ, because in your heart the cells turn off all the brain genes and the blood genes, while switching on all the heart genes. But how do your heart cells know they are going to be heart cells?

The video puts forward a possible explanation for how germ cells know they are going to become germ cells, I haven’t heard this explanation before, but it’s a good one. There are a few other ways cells are told what they are going to be when they grow up, but that is a topic for another day (and probably another video!)

Hat tip to The Loom. Cheers!






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