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Cartilage-Hair Hypoplasia

Page history last edited by Ashley Hough 11 years, 6 months ago
  1. What gene is affected to cause this disease?

          In Cartilage-Hair Hypoplasia, the RMRP gene is affected.


    2.   On which chromosome is the gene located?  Find an image of the chromosome or a human karyotype and identify the location           of the gene.

          The RMRP gene is located on Chromosome 9, as show in the image below where the yellow arrow indicates the location of RMRP.

  1. What is the function of the "normal" gene?  What protein/enzyme does it code for?  What is the function of this protein/enzyme?

    The function of the "normal" gene is to produce noncoding RNA, which in turn binds to proteins and forms Mitochondrial RNA-processing endoribonuclease, or RNase MRP. This enzyme helps DNA in the motochondria replicate and processes ribosomal RNA, which helps turn amino acids into proteins in the translation process

  1. What are the symptoms of the disease?  How is this related to the function of the protein? 

          The symptoms of Cartilage-Hair Hypoplasia are: immune deficiency, fine/sparse hair, and short stature along with other skeletal           abnormalities, light-colored hair and light-colored skin. This is related to the function of the protein because when the RNA is           unstable, it cannot bind to proteins and its control in the cell cycle and functions within a cell are disrupted, leading to the           symptoms associated with cartilage-hair hypoplasia. 


  1. What type of mutation (or other chromosomal error) is often associated with this disease?

    People with cartilage-hair hypoplasia have a guanine substituted for the adenine at position 70 in the RMRP gene.  

  1. Why is the non-“normal” form of the gene unable to produce a functional protein/enzyme? 

          The non-"normal" form of the gene is still able to produce noncoding RNA, but this RNA is altered just enough to make it unable           to bind to different proteins and disrupts the RNase MRP complex in the cells.


  1. What is the pattern of inheritance of this disease? 

          This disease is inherited in an autosomal recessive pattern.


  1. What is the frequency of this disease in the population?  Frequency of carriers? 

          Cartilage-Hair Hypoplasia is most frequent among the Old Order Amish population and affects about 1 in 1,300 babies. Among           people of Finnish descended people, it is about 1 in 20,000 people.


  1. What are currently available treatment options? 

          Currently, supportive forms of treatment are available in which antibiotics can be given to fight infections people with this disease           can be more susceptible to as a result of their suppressed immune system. 


  1. If there is an effective treatment available, how does this work?  If there is none, why has it been difficult to develop an effective treatment?  List at least one support organization for those with the disease and their families.    

          A form of treatment depends on whether the affected person has T-cell immunoeficiency or not. If they do, this can be treated           with a bone marrow transplant. Antibiotics can be given out to fight the infections and diseases they are more susceptible to           getting such as chickenpox.

          http://www.lpaonline.org/mc/page.do?sitePageId=37298&orgId=lpa Little People of America is a web-based organization for           people suffering from diseases that cause short stature and dwarfism, from CHH to Achondroplasia. It provides information about           the various diseases, links to other support and research organizations, and information about adoption, scholarships, and           medical support.


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