Cheryll Tickle facts for kids

Cheryll Anne Tickle, born on January 18, 1945, is a British scientist. She is famous for her work in developmental biology. This field studies how living things grow and develop. Dr. Tickle especially researched how limbs (like arms and legs) form in animals with backbones, starting from a tiny egg. She is now a professor at the University of Bath.

Education and Early Career

Cheryll Tickle studied at the University of Cambridge. She earned her master's degree there in 1967. Later, she received her PhD from the University of Glasgow in 1970. Her PhD research looked at how cells arrange themselves in groups.

After her PhD, Dr. Tickle went to Yale University in the United States. She worked as a postdoc there. She then returned to London and worked at the Middlesex Hospital Medical School. Later, she became a professor at University College London. In 1998, she moved to the University of Dundee. She joined the University of Bath in 2007.

Understanding How Limbs Form

Dr. Tickle's main research explores how a single cell, like a fertilized egg, grows into a complete living thing. This process is called embryogenesis.

Cell Sorting and Limb Development

Early in her career, Dr. Tickle became interested in "cell sorting." This is when cells are separated and then put back together. Scientists observed how these cells would naturally rearrange themselves into organized structures.

After her time at Yale, Dr. Tickle focused on how cells sort themselves during the development of limbs. She worked with chicken embryos. She believed that if embryonic limb cells were mixed up, they would still arrange themselves into the correct pattern.

The Role of the ZPA in Limb Growth

In 1969, another scientist, John Saunders, found two important areas in a developing limb:

• The apical ectodermal ridge (AER)
• The zone of polarizing activity (ZPA)

These areas are key for a limb to grow properly. Dr. Tickle focused on how the ZPA controls limb development. She especially looked at how it affects the front-to-back (anterior-posterior) axis of a limb. This axis determines where the thumb or pinky finger will be.

Morphogens and Digit Formation

Dr. Tickle's colleague, Lewis Wolpert, suggested that the ZPA releases a special chemical called a morphogen. This morphogen creates a "concentration gradient." This means there's more of the chemical closer to the ZPA and less further away.

Cells in different parts of the limb bud would get different amounts of this morphogen. This information would tell them what to develop into. For example, cells closest to the ZPA would form one type of digit, while cells further away would form another.

Dr. Tickle's experiments on chicken wings supported this idea. She found that the type of digit that formed depended on its distance from the ZPA. Cells closer to the ZPA formed digit 4 (like a pinky finger). Cells furthest away formed digit 2 (like an index finger). This was a big step in understanding how limbs develop.

Chemical Signals in Limb Development

In 1976, biochemist Bruce Alberts suggested using tiny beads in experiments. Dr. Tickle and her team soaked these beads in extracts from the ZPA. They then placed the beads on developing chicken limbs. This helped them study how different chemicals affect growth.

In the early 1980s, Dr. Tickle's lab made an important discovery. They found that retinoic acid could act like the ZPA signal. When beads soaked in retinoic acid were applied, they could cause limb duplication.

By 1990, scientists found that many genes important for development in vertebrates (like chickens) were similar to genes in fruit flies. Dr. Tickle worked with other scientists to study these genes, called Hox genes, in developing chicken wings. They found that if a limb was duplicated using retinoic acid, the pattern of these Hox genes was also copied.

Dr. Tickle also worked with Gail Martin and Lee Niswander in 1994. They discovered that fibroblast growth factors (FGFs) are used by the AER for signaling. They also found that bone morphogenetic proteins (BMPs) are involved in the ZPA signaling.

To test this, Dr. Tickle used her bead method. She removed the AER from a chick wing bud. Then, she replaced it with beads soaked in FGF. This helped the chicken wing develop correctly. This was a major finding!

One of Dr. Tickle's students found that even a few hours of FGF signaling could cause a new limb to form. This showed that FGF signaling must turn off once a limb is fully developed. If it doesn't, extra digits or other problems could happen.

Awards and Recognition

Dr. Cheryll Tickle has received many important awards for her work:

• She became a Fellow of the Royal Society (FRS) in 1998.
• She was elected a Fellow of the Royal Society of Edinburgh (FRSE) in 2000.
• She became a Fellow of the Academy of Medical Sciences (FMedSci) in 2001.
• She joined the European Molecular Biology Organisation in 2001.
• In 2004, the University of St. Andrews gave her an honorary doctorate.
• In 2005, she was named a Commander of The Most Excellent Order of the British Empire (CBE).

Her nomination for the Royal Society praised her for showing how the ZPA signal affects digit patterns. It also highlighted her discovery that retinoic acid can copy this signal. Her work also showed that FGF is essential for limb development.

Personal Life

Cheryll Tickle married John Gray in 1979.