Barakat-Perenthaler syndrome is a rare neurodevelopmental genetic disorder, presenting with a severe epileptic encephalopathy, developmental delay, Intellectual disability, progressive microcephaly and visual disturbance. It is listed by the standard reference, Online Mendelian Inheritance in Man (OMIM) as #618744. [1] and classified as EPILEPTIC ENCEPHALOPATHY, EARLY INFANTILE, 83; EIEE83. It was first described in 2019 by Dr. Stefan Barakat and his team at the Erasmus University Medical Center in Rotterdam in the journal Acta Neuropathologica ; [2] the most recent reviews were published in Epilepsy Currents . [3] and Trends in Endocrinology and Metabolism [4]
Barakat-Perenthaler syndrome OMIM 618744 has so far been identified in more than 40 individuals, of which 22 individuals from 15 families were published., [1] According to OMIM's review of all published cases [1] and the initial study from Perenthaler et al, [2] all children presented in early life with severe and intractable epileptic seizures. Severe developmental delay was found in all individuals, with basically absence of all developmental milestones. [1] [2] Children were unable to roll over or sit, did not develop speech, had absent visual tracking and most cases required gastro-intestinal tube feeding due to severe orofacial hypotonia. [1] [2] Other neurological features included infantile epileptic spasms, axial hypotonia, peripheral spasticity and/or hyperreflexia, and a few cases showed dystonia. [1] [2] Head circumference decreased progressively over time. [1] [2] MRI brain imaging did not detect major structural brain abnormalities, but showed progressive brain atrophy over time. [1] [2] Mild dysmorphic features were noted amongst several individuals, including a sloping forehead, suture ridging, bitemporal narrowing, high hairline, arched eyebrows, pronounced philtrum, and a relatively small mouth and large ears. [2] Most children died early in life [1] [2]
Barakat-Perenthaler syndrome [1] is an autosomal recessive disorder and is caused by a recurrent homozygous mutation [5] of the UDP-glucose pyrophosphorylase (UGP2) gene. [6] [7] UGP2 encodes an essential protein in nucleotide sugar metabolism, which catabolizes the conversion of glucose-1-phosphate to UDP-glucose. [8] [9] In humans, two functionally equivalent protein isoforms are encoded by the UGP2 gene, a longer one (isoform 1) [10] and a slightly shorter one (isoform 2), [11] that only differ by 11 amino acids at the N-terminal. [12] The recurrent mutation (chr2:64083454A>G) [13] identified in all patients with the syndrome affects the start codon of the shorter protein isoform. [1] [2] Hence, the shorter isoform can no longer be produced in affected individuals. [2] It was shown by Barakat and colleagues that the shorter UGP2 isoform is predominantly expressed in human brain. [2] Therefore, the recurrent mutation leads to a brain-specific depletion of the essential UGP2 protein, resulting in altered glycogen metabolism, upregulated unfolded protein response and premature neuronal differentiation which likely cause the disease symptoms. [2]
A complete loss of UGP2 isoform 1 and isoform 2 in human embryonic stem cells prevented the formation of functional heart and blood cells in in vitro differentiation experiments. Hence it is likely that bi-allelic loss-of-function of all UGP2 isoforms is incompatible with life in humans; in agreement with this, no bi-allelic loss-of-function variants affecting both protein isoforms are reported in the gnomAD database. [14] The syndrome is therefore an example of a disease caused by the loss of expression of a tissue relevant isoform of an essential gene. [2] Recently, bi-allelic loss of UDP-Glucose 6-Dehydrogenase (UGDH), another gene implicated in nucleotide sugar metabolism, [15] was also shown to cause a similar severe epileptic encephalopathy syndrome, referred to by OMIM as Jamuar syndrome (OMIM #618792), [16] [17] showing that nucleotide sugar metabolism can be more broadly implicated in epilepsy.
Barakat and colleagues showed that all identified affected individuals harboring the recurrent mutation shared the same haplotype, suggesting a founder effect and a common ancestor. [2] The mutation was estimated to have originated 26 generations (approximately 600 years) ago. [2] Most cases of Barakat-Perenthaler syndrome could be linked to the Balochistan region (consisting of parts of Iran, Pakistan, India). Since Dutch traders were active in that region in the 17th century, [18] this could be an explanation for the introduction of the founder mutation into the Dutch population, from which the first case was described [2]
So far, no treatment is available for Barakat-Perenthaler syndrome. [19]
Mitochondrial myopathies are types of myopathies associated with mitochondrial disease. Adenosine triphosphate (ATP), the chemical used to provide energy for the cell, cannot be produced sufficiently by oxidative phosphorylation when the mitochondrion is either damaged or missing necessary enzymes or transport proteins. With ATP production deficient in mitochondria, there is an over-reliance on anaerobic glycolysis which leads to lactic acidosis either at rest or exercise-induced.
Myophosphorylase or glycogen phosphorylase, muscle associated (PYGM) is the muscle isoform of the enzyme glycogen phosphorylase and is encoded by the PYGM gene. This enzyme helps break down glycogen into glucose-1-phosphate, so it can be used within the muscle cell. Mutations in this gene are associated with McArdle disease, a glycogen storage disease of muscle.
UTP—glucose-1-phosphate uridylyltransferase also known as glucose-1-phosphate uridylyltransferase is an enzyme involved in carbohydrate metabolism. It synthesizes UDP-glucose from glucose-1-phosphate and UTP; i.e.,
Ohtahara syndrome (OS), also known as Early Infantile Developmental & Epileptic Encephalopathy (EIDEE) is a progressive epileptic encephalopathy. The syndrome is outwardly characterized by tonic spasms and partial seizures within the first few months of life, and receives its more elaborate name from the pattern of burst activity on an electroencephalogram (EEG). It is an extremely debilitating progressive neurological disorder, involving intractable seizures and severe intellectual disabilities. No single cause has been identified, although in many cases structural brain damage is present.
Inborn errors of carbohydrate metabolism are inborn error of metabolism that affect the catabolism and anabolism of carbohydrates.
Legius syndrome (LS) is an autosomal dominant condition characterized by cafe au lait spots. It was first described in 2007 and is often mistaken for neurofibromatosis type I. It is caused by mutations in the SPRED1 gene. It is also known as neurofibromatosis type 1-like syndrome.
Transmembrane protein 241 is a ubiquitous sugar transporter protein which in humans is encoded by the TMEM241 gene.
The coiled-coil domain containing 142 (CCDC142) is a gene which in humans encodes the CCDC142 protein. The CCDC142 gene is located on chromosome 2, spans 4339 base pairs and contains 9 exons. The gene codes for the coiled-coil domain containing protein 142 (CCDC142), whose function is not yet well understood. There are two known isoforms of CCDC142. CCDC142 proteins produced from these transcripts range in size from 743 to 665 amino acids and contain signals suggesting protein movement between the cytosol and nucleus. Homologous CCDC142 genes are found in many animals including vertebrates and invertebrates but not fungus, plants, protists, archea, or bacteria. Although the function of this protein is not well understood, it contains a coiled-coil domain and a RINT1_TIP1 motif located within the coiled-coil domain.
Transmembrane Protein 176B, or TMEM176B is a transmembrane protein that in humans is encoded by the TMEM176B gene. It is thought to play a role in the process of maturation of dendritic cells.
Solute carrier family 25 member 22 is a protein that in humans is encoded by the SLC25A22 gene. This gene encodes a mitochondrial glutamate carrier. Mutations in this gene are associated with early infantile epileptic encephalopathy. Expression of this gene is increased in colorectal tumor cells.
BEND2 is a protein that in humans is encoded by the BEND2 gene. It is also found in other vertebrates, including mammals, birds, and reptiles. The expression of BEND2 in Homo sapiens is regulated and occurs at high levels in the skeletal muscle tissue of the male testis and in the bone marrow. The presence of the BEN domains in the BEND2 protein indicates that this protein may be involved in chromatin modification and regulation.
The Family with sequence similarity 149 member B1 is an uncharacterized protein encoded by the human FAM149B1 gene, with one alias KIAA0974. The protein resides in the nucleus of the cell. The predicted secondary structure of the gene contains multiple alpha-helices, with a few beta-sheet structures. The gene is conserved in mammals, birds, reptiles, fish, and some invertebrates. The protein encoded by this gene contains a DUF3719 protein domain, which is conserved across its orthologues. The protein is expressed at slightly below average levels in most human tissue types, with high expression in brain, kidney, and testes tissues, while showing relatively low expression levels in pancreas tissues.
C2orf81 is a human gene encoding protein c2orf81, which is predicted to have nuclear localization.
SYNGAP1-related intellectual disability is a monogenetic developmental and epileptic encephalopathy that affects the central nervous system. Symptoms include intellectual disability, epilepsy, autism, sensory processing deficits, hypotonia and unstable gait.
Lysine-rich nucleolar protein 1 (KNOP1) is a protein which in human's is encoded by the KNOP1 gene. Aliases for KNOP1 include TSG118, C16orf88, and FAM191A.
THAP domain-containing protein 3 (THAP3) is a protein that, in Homo sapiens (humans), is encoded by the THAP3 gene. The THAP3 protein is as known as MGC33488, LOC90326, and THAP domain-containing, apoptosis associated protein 3. This protein contains the Thanatos-associated protein (THAP) domain and a host-cell factor 1C binding motif. These domains allow THAP3 to influence a variety of processes, including transcription and neuronal development. THAP3 is ubiquitously expressed in H. sapiens, though expression is highest in the kidneys.
NADP-dependent oxidoreductase domain-containing protein 1 is a protein that in humans is encoded by the NOXRED1 gene. An alias of this gene is Chromosome 14 Open Reading Frame 148 (c14orf148). This gene is located on chromosome 14, at 14q24.3. NOXRED1 is predicted to be involved in pyrroline-5-carboxylate reductase activity as part of the L-proline biosynthetic pathway. It is expressed in a wide variety of tissues at a relatively low level, including the testes, thyroid, skin, small intestine, brain, kidney, colon, and more.
SLC13A5 citrate transporter disorder, or SLC13A5 Epilepsy, is a rare genetic spectrum disorder that presents with neurological symptoms. Symptoms include severe seizures, ataxia, dystonia, teeth hypoplasia, poor communication skills, difficulty standing or walking, as well as developmental delay. Other names associated with SLC13A5 Epilepsy include SLC13A5 Citrate Transporter Disorder, Citrate Transporter Disorder, SLC13A5 Deficiency, Early Infantile Epilepsy Encephalopathy 25 (EIEE25), Developmental Epilepsy Encephalopathy 25 (DEE25), and Kohlschutter-Tonz Syndrome (non-ROGDI).
EVA1C is a transmembrane protein in humans that is encoded by the EVA1C gene on Chromosome 21. The EVA1C protein is thought to be involved in herapin binding activity. In addition, the gene is thought to be associated with diseases such as X-Linked Intellectual Disability-Short Stature-Overweight Syndrome.
Transmembrane protein 19 is a protein that in humans is encoded by the TMEM19 gene.