Understanding CLN7
Understanding CLN7, a Subtype of Batten Disease
Batten diseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan. is a group of rare neurodegenerative diseases, also known as neuronal ceroid lipofuscinoses (NCLs)Refers to a group of conditions that affect the nervous system. Signs and symptoms vary widely between the forms but generally include a combination of dementia, vision loss, and epilepsy.. Each NCL disease is classified by the gene that causes it. The name of each gene begins with CLN – ceroid lipofuscinosis, neuronal – followed by a unique number that indicates the subtype.
Changes in the normal function of these genes, due to pathogenic variantsA change in DNA that causes disease., lead to disruption of normal protein function. This disruption results in lysosomal dysfunction, and the accumulation of molecules in the cells throughout the body.
The symptoms, severity, onset, and progression across the subtypes vary. Both males and females are affected. The subtypes of Batten disease can be found here.
The CLN7 subtype of Batten disease is caused by a variantA variant is a change in DNA. A variant may or may not cause disease. The following modifiers describe the variant: (i) pathogenic, (ii) likely pathogenic, (iii) uncertain significance, (iv) likely benign, or (v) benign depending on whether or not the variant causes disease. For example, a “pathogenic variant” may cause disease. The term “variant” has replaced the term “mutation.” in the CLN7 gene, also called the MFSD8 gene, which leads to disruption of normal CLN7 protein function. The exact function of this protein is unknown. Individuals with CLN7 typically develop neurological signs and symptoms in early childhood, such as seizures, progressive deterioration in intellectual and motor capabilities, and loss of vision. The disease ultimately leads to a shortened lifespan.
Source: Batten Disease Fact Sheet. (2019, June 24). Retrieved August 8, 2019, from link.
History of Batten Disease
Batten disease, a common name for a rare class of diseases called neuronal ceroid lipofuscinoses (NCLs), was first described in 1903 by British neurologist and pediatrician Frederick Batten.
Today, there are 13 known subtypes of Batten disease. Symptoms and disease management for each subtype of Batten disease vary, although several subtypes share similar features and symptoms. Batten disease originally referred specifically to the juvenile-onset type of NCL, but now has been used more generally to describe all types of NCLs. Batten disease affects an estimated 2-4 out of every 100,000 children in the United States.
History of CLN7 (Neuronal Ceroid Lipofuscinosis 7)
CLN7 was first reported in 2004; to date, more than 70 known cases of CLN7 exist in the scientific literature. CLN7 affects children globally, across ethnicities and races, and was first diagnosed in the Turkish population.
CLN4 and CLN9 genes have still not been identified.
Sources:
- Batten Disease Fact Sheet. (2019, June 24). Retrieved July 31, 2019, from link.
- CLN5 disease. (2019, July 16). Retrieved July 31, 2019, from link.
- Frederick Eustace Batten. (n.d.). Retrieved July 31, 2019, from link.
- Batten Disease Support and Research Association. (2000). Batten Disease Neuronal Ceroid Lipofuscinosis (Publication). Retrieved August 14, 2019, from link.
- CLN1 Disease, infantile onset and others. (n.d.). Retrieved August 14, 2019, from link.
- CLN10 disease, congenital, neonatal and late infantile. (n.d.). Retrieved August 14, 2019, from link.
- CLN2 Disease, Late Infantile. (n.d.). Retrieved August 14, 2019, from link.
- CLN8 Disease, EPMR and late infantile variant. (n.d.). Retrieved August 14, 2019, from link.
- McKusick, V. A. (1997, April 28). CEROID LIPOFUSCINOSIS, NEURONAL, 6; CLN6. Retrieved August 14, 2019, from link.
- Types of Batten Disease. (n.d.). Retrieved August 14, 2019, from link.
- CLN7 disease. (2019, July 16). Retrieved July 31, 2019, from link.
- CLN7. (2010, February). Retrieved July 31, 2019, from link.
- CEROID LIPOFUSCINOSIS, NEURONAL, 7; CLN7. (2016, December 8). Retrieved July 31, 2019, from link.
How CLN7 Disease Affects the Body
CLN7 disease affects children both cognitively and physically. Symptoms of the disease may include:
Science Behind CLN7 Disease
The underlying cause of CLN7 disease is found in an individual’s genetic code. In humans, each cell contains 23 pairs of chromosomes for a total of 46: 23 from their mother and 23 from their father. The first 22 pairs of chromosomes are autosomesAny chromosome in a cell that is not an X or Y sex chromosome. The average person has 22 pairs of autosomes (44 autosomes in total) in each cell that define the genetic make-up, or DNA, of the being. These chromosomes store thousands of genes and they are inherited from the beings’ parents. In addition to the 22 pairs of autosomes (44 total), beings also have one pair (2 total) sex chromosomes (X and Y in a male, and X and X in a female)., and they look the same in both males and females. The 23rd pair are sex chromosomes, which are different between males and females. Females have two copies of the X chromosomes (XX) and males have one X and one Y chromosome (XY). A variant in a gene on one of the first 22 autosomes can lead to an autosomalInheritance characteristic where a gene is located on a numbered, non-sex chromosome. These are found on one of the 22 pairs of (44 total) autosomal chromosomes in a human body where DNA is stored. This is one of several ways that a trait, disorder, or disease can be passed down through families. These chromosomes are not the sex (X or Y) chromosomes. disease.
Autosomal recessive is one of several ways that a disorder or disease is passed down through families. An autosomal recessive disorder occurs when a child inherits two copies of a mutated gene, one from the mother and one from the father. The biological parents, known as carriers, each carry only one copy of the mutated gene, and usually do not show symptoms of the disease.
CLN7 disease is inherited in an autosomal recessive pattern, meaning both copies of the CLN7 gene variant (one from each parent, or carrier) must be present for the child to be diagnosed with CLN7 disease.
Healthy CLN7 Gene
A healthy CLN7 gene provides the body with instructions for building the CLN7 protein. Although the exact function of the protein is unknown, it is thought to transport molecules across the lysosomal membrane — resulting in normal cellular function.
CLN7 Variant
People with CLN7 disease have a variant on the CLN7 gene, also known as the MFSD8 gene, located on chromosome 4. When there is a variant or mutationA mutation is any inherited genetic change. The term “mutation” is being replaced by the term “variant.” in the CLN7 gene, the body creates a non-functional CLN7 protein that cannot transport molecules across the lysosomal membrane, resulting in lysosomal dysfunction. The lysosomeSpecialized vesicles within cells that digest large molecules, breaking down excess waste products of the cell with the help of enzymes. Lysosomes may also be used to destroy invading viruses and bacteria., when unable to function properly, causes an accumulation of molecules throughout the body and causes cell death.
Although the CLN7 protein is expressed throughout the body, nerve cells seem to be the most impacted, leading to the central nervous system-related signs and symptoms seen in patients who have CLN7.
Sources:
- Sharifi, A., Kousi, M., Sagné, C., Bellenchi, G. C., Morel, L., Darmon, M., Hůlková, H., Ruivo, R., Debacker, C., El Mestikawy, S., Elleder, M., Lehesjoki, A. E., Jalanko, A., Gasnier, B., & Kyttälä, A. (2010, Nov.). Expression and lysosomal targeting of CLN7, a major facilitator superfamily transporter associated with variant late-infantile neuronal ceroid lipofuscinosis. Human Molecular Genetics, 19(22): 4497–4514. Retrieved December 17, 2019, from link.
- Types of Batten Disease. (n.d.). Retrieved August 14, 2019, from link.
- CLN7 disease. (2019, July 16). Retrieved July 31, 2019, from link.
- Neuronal ceroid lipofuscinosis 7. (n.d.). Retrieved July 31, 2019, from link.
CLN7 is a subtype of Batten diseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan. with late infantile onset, which means that the signs and symptoms of CLN7 begin to show during early childhood years. Children living with CLN7 will often experience the first signs and symptoms of the disease between the ages of 2 and 7 years old. After disease onset occurs, the symptoms will continue to progress.
Birth Through Age 7
Children with CLN7 typically experience normal development until about the age of 2 years. Initial common signs and symptoms may include:
- Vision deterioration
- Recurrent seizures, or epilepsy
- Twitching movements (myoclonusBrief, shock-like jerks or twitching of a muscle (myoclonus).)
- Difficulty sleeping
- Motor clumsiness
- Loss of motor skills that were previously acquired (developmental regressionWhen a child loses an acquired function, milestone or fails to progress beyond a prolonged plateau after a period of relatively normal development.)
We noticed Gabriela was having more frequent seizures. They were always quick, and it looked like she was just nodding her head.
- Sara, mother of Gabriela, a CLN7 patient*
*Sara's daughter, Gabriela, lost her fight against CLN7. Sara would like her story to remain as a legacy to her life.
Adolescent years
As the disease continues to progress through adolescent years, other symptoms may become apparent:
- Cognitive decline and memory loss
Aashi can still see light and shadow, but her vision is limited. It was the next thing she lost after her motor skills. She’s usually in high spirits and will hum or make noises when she hears songs or nursery rhymes that she knows.
- Rishi, father of daughter living with CLN7
Childhood Years
Signs and symptoms may appear more severe during this stage. The signs that are most commonly seen during this time may include:
- Progressive loss of vision
- Difficulty coordinating movements (ataxiaThe difficulty with or loss of muscle coordination and bodily movements.)
- Loss of gross motor function, including the ability to walk
- Development of a speech impairment with gradual loss of speech abilities
Signs & Symptoms Reported by Caregivers
While the signs, symptoms, and age of onset of CLN7 may vary and can progress differently in each individual, there are common signs and symptoms that are consistent across people living with CLN7. The examples below come from parents of children with CLN7.
- Progressive loss of vision (reluctance to step off curbs, squinting to look at pictures, reads a book too close to face, sees things that aren’t there, especially at night)
- Attention disturbances, cognitive delay, and memory loss (isn’t meeting milestones, slow to respond verbally)
- Seizures (appearing to nod off, looks like they are startled awake, twitches and tremors)
- Clumsiness and challenges with gross motor function or coordination of movement (lack of agility, reluctance to run, difficulty hopping on one foot, tripping, falling)
- Deterioration of fine motor skills (challenges with scissors, needing a fat crayon instead of a pencil, difficulty picking up small objects)
- Speech impairment (uses simple words to express themselves, need support for missing words or letters)
Sources:
- Neuronal ceroid lipofuscinosis 7 (n.d.). Retrieved August 16, 2019, from link.
- Batten Disease Fact Sheet. (2019, June 24). Retrieved July 31, 2019, from link.
- Types of Batten Disease. (n.d.). Retrieved August 14, 2019, from link.
- CLN7 disease. (2019, July 16). Retrieved July 31, 2019, from link.
- Kousi, M., Siintola, E., Dvorakova, L., Vlaskova, H., Turnbull, J., Topcu, M., Yuksel, D., Gokben, S., Minassian, B.A., Elleder, M., Mole, S.E., Lehesjoki, A.E. (2009). Mutations in CLN7/MFSD8 are a common cause of variant late-infantile neuronal ceroid lipofuscinosis. Brain, 132(3): 810–819. Retrieved December 17, 2019, from link.
- Field resource conducted by Neurogene and Ten Bridge Communications, August 2019.
Obtaining a definitive genetic diagnosis is an important first step in seeking appropriate care and treatment, learning about potential research or therapies that may become available, and preparing for the future. Patients and their families should consider discussing the implications of obtaining a diagnosis of CLN7 with their physician and a genetic counselor or other specialists who are familiar with the disease management of CLN7.
If you believe your child is showing signs or symptoms of CLN7, tests are available for a physician or other healthcare professional to order to confirm a diagnosis.
Many academic and commercial labs offer genetic testing. Testing for CLN7 may not be included in standard testing panels; however, upon request, a diagnostic genetic test including an expanded exome sequencing panelThrough this diagnostic test performed by a geneticist, the exome -- a sequence of all exons of protein coding genes in the human genome -- can be captured and analyzed with the intention of identifying a disease with a genetic component. for CLN7 can confirm a diagnosis. Your physician can help you navigate the process or refer you to a geneticist.
Patient organizations also provide helpful information and resources for genetic testing. For additional information on genetic testing and to find possible sources for testing, you can refer to these Batten disease advocacy organizations.
A representative is available to help you:
A Clinician's Perspective on Diagnosis:
“CLN5 and CLN7 are two very rare forms of
Batten diseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan., both marked by regression of motor and language skills, as well as seizures, during childhood years. While signs and symptoms for both are similar to other types of Batten disease, these subtypes are not currently tested within a standard panel. If your child is experiencing motor and language regression, consider speaking to your healthcare provider about an expanded exome sequencing panelThrough this diagnostic test performed by a geneticist, the exome — a sequence of all exons of protein coding genes in the human genome — can be captured and analyzed with the intention of identifying a disease with a genetic component.. With a positive diagnosis, children may be eligible to participate in research that could help the community better understand Batten disease.”
Elizabeth Berry-Kravis, M.D., Ph.D.,
Pediatric Neurologist and Professor
Rush University Medical Center
While there is currently no treatment for children living with CLN7, there are a number of specialists with expertise who can help families affected by CLN7 manage their disease and its symptoms.
People living with CLN7 benefit from having a team of healthcare professionals and assistive devices to help manage the progressive and variable impact of their disease. The daily needs of an individual with CLN7 can be supported by some or all of the following healthcare providers. These needs may evolve as a child moves into adulthood or as the disease progresses.
Click on each circle below for more information about the role each healthcare provider may play to support the daily needs of an individual living with CLN7:
In addition to the care team that can help to manage the various symptoms associated with CLN7 disease, people caring for a child with CLN7 disease may also find support through social and educational plans. These plans support the family as symptoms progress.
Sources:
- Batten DiseaseBatten disease is the common name for a broad class of rare, inherited disorders or diseases of the nervous system also known as neuronal ceroid lipofuscinoses, or NCLs. In these diseases, a defect in a specific gene triggers a cascade of problems that interferes with a cell’s ability to recycle certain molecules. The disease has several forms that share some of the same features and symptoms but vary in severity and age when symptoms first begin to appear. Each form is caused by a variant in a different gene. Although “Batten disease” originally referred specifically to the juvenile-onset form of NCL, the term Batten disease is increasingly used to describe all forms of NCL. The disease ultimately leads to shortened lifespan. Fact Sheet. (2019, May 14). Retrieved July 30, 2019, from link.
- CLN7 disease. (2019, July 16). Retrieved July 31, 2019, from link.
