CRI DU CHAT SYNDROME by: Olivia Gerald 12|o9|2011 Mrs. Abrams Period 3A Life Science

What is Cri-du-Chat Syndrome? Cri-du-chat is French for “cry of the cat”, referring to the distinctive, high-pitched, catlike cry made by children afflicted by this disorder. Caused by partial deletion of chromosome 5p. Becomes less noticeable as the child gets older, making it difficult for doctors to diagnose cri-du-chat after age two. Partial deletion of the 5 pair chromosome.

The Cause Cri-du-chat is caused by a deletion on the short arm of chromosome 5p – the length of the deletion may vary. Multiple genes are missing as a result of this deletion, and each may contribute to the symptoms of the disorder. One of the deleted genes known to be involved is HTERT (human telomerase reverse transcriptase). HTERT helps to keep the information in DNA functioning properly. If HTERT is damaged, mental illnesses such as cri-du-chat occur.

SYMPTOMS Microcephaly Low-set ears Normal brain size Brain size with cri-du-chat TOP: Normal ear position/size BOTTOM: Ear position/size with cri-du-chat

SYMPTOMS Babies with cri-du-chat are usually small at birth, and may have respiratory problems. Often, the larynx doesn’t develop correctly, which causes the signature catlike cry. Mental retardation: the more extensive the deletion is of chromosome 5p, the more severe this symptom. Small head (microcephaly). Small jaw (micrognathia). Downward slant of the eyes. Wide-set eyes. Abnormally shaped/positioned ears. Webbed fingers or toes. Single line in the palm of the hand (simian crease). Hanging skin in front of the ears. Slow or incomplete development of basic skills.

Inheritance of Cri-du-Chat The deletion that causes cri-du-chat syndrome is caused by a dominant trait. CTNND2 is an important gene that is lost when a portion of the 5 pair chromosome is deleted. CTNND2 gene usually makes the delta catenin protein. This protein works in the nervous system and helps with cell movement. The loss of CTNND2 may cause severe brain damage in some patients. CTNND2 gene under a microscope. Delta catenin protein.

Inheritance of Cri-du-Chat In this example: P GENERATION: A= dominant allele for a person with cri-du-chat. a= recessive allele for a person without cri-du-chat. F1 GENERATION: All offspring have the cri-du-chat syndrome because they all inherit dominant allele A. a A Aa

Diagnosis & Treatment Doctors most often identify cri-du-chat by looking at the patient’s symptoms. The most common symptoms are the infant's cat-like cry, microcephaly (small head/brain), poor muscle tone, and mental retardation. Another method of diagnosing cri-du-chat syndrome takes place while the baby is still in its mother's womb. Doctors can either test a tiny sample of tissue from outside the sac where the baby develops, or they can test a sample of the amniotic fluid – the protective liquid in the womb from which a baby gets nourishment. There is no specific treatment available for this disorder so medical care is focused on the symptoms. Physical therapy is recommended to strengthen the muscles. To increase communication skills, a speech therapist can help the child learn to use sign language.

Statistics Approximately 90% of cases of cri-du-chat syndrome result from a randomly-occurring deletion. The remaining 10% occurs purely by inheritance. Cri-du-chat syndrome occurs in an estimated 1 in 20,000 to 50,000 newborns. Cri-du-chat can occur in all races and in both genders, although there is a slight female predominance. The male to female ratio is 3:4. Approximately 30% of infants with cri-du-chat have heart defects. About 1/3 of infants lose the catlike cry at age 2.

Interesting Facts The geneticist Jerome Lejeune identified cri-du-chat syndrome in 1963. He also discovered the genetic abnormality that causes Down syndrome. In 80% of cri-du-chat cases, the chromosome carrying the deletion comes from the father’s sperm rather than the mother’s eggs. If pairs of chromosomes don’t line up correctly during metaphase in meiosis, the structure of a chromosome can be changed. When this happens with chromosome 5, it causes cri-du-chat. Cri-du-chat is the most common syndrome caused by deletion.

BIBLIOGRAPHY WEBSITES: http://medical-dictionary.thefreedictionary.com/cri+du+chat+syndrome http://ghr.nlm.nih.gov/condition/cri-du-chat-syndrome http://en.wikipedia.org/wiki/Cri_du_chat BOOKS: Encyclopedia Britannica Webster’s Encyclopedia