1. Lamellar Ichthyosis Fadel A. Sharif
Lamellar Ichthyosis (LI) is a rare, hereditary skin condition characterized by dry, thick, fish-like scaling of the skin. Ichthy means "fish" in Greek; osis = disease condition and lamellar means "thin layer."

2. Partial Pedigree
The newborn is born encased in a collodion membrane

3. Derived from two Greek words meaning "fish" and "disease“.
Ichthyosis
Derived from two Greek words meaning "fish" and "disease“.
Dermatological disease that is represented by thick, scaly skin.
Caused by an abnormality in skin formation that results in drying and scaling.
At least 20 types, variable severity.
Inherited and acquired forms exist.
Acquired ichthyoses
The mildest form of acquired ichthyosis is called xeroderma, or dry flaky skin. It is not associated with any systemic diseases. Xeroderma occurs most often on the lower legs of middle-aged and elderly adults during cold weather, or on the lower legs of people who bathe too often. It is characterized chiefly by mild or moderate itching.
Ichthyosis may also be an early symptom of such disorders as AIDS, lymphoma, hypothyroidism, or leprosy. In these cases the ichthyosis is most noticeable on the patient's trunk and legs.
A few rare cases of acquired ichthyosis have been attributed to the use of certain drugs, specifically cimetidine (Tagamet), triparanol (Metasqualene), dixyrazine (a phenothiazine derivative used as an antipsychotic), nicotinic acid (vitamin B3, butyrophenone antipsychotics (Haldol, Inapsine, Orap), and clofazimine (Lamprene).

4. Lamellar Ichthyosis (MIM 242300)
Autosomal recessive (ARCI-1)
Panethnic, rare (1 in 200,000)
Apparent at birth and is present throughout life
Genetically heterogenous (6 genes, 5 of them identified: TGM1 (14q11.2), ABCA12 (2q34), 19p12-q12, 19p13; ALOXE3-ALOX12B (17p13), ichthyin (5q33)
More than 90% mutant TGM1 gene (14q11.2)
Infants affected with LI are born encased in a hyperkeratotic translucent membrane, known as collodion baby, and within 2 weeks develop large, thick, brownish lamellar scales with minimal erythema. Additionally, LI is associated with crumpled ears, alopecia, eclabium, and ectropion. Lamellar Ichthyosis (LI) is a rare, hereditary skin condition characterized by dry, thick, fish-like scaling of the skin. Ichthy means "fish" in Greek and lamellar means "thin layer."

5. Lamellar Ichthyosis: Main Features
Infant is born encased in a hyperkeratotic translucent membrane, known as “collodion baby”.
Crumpled ears, alopecia, eclabium, and ectropion.
Infants affected with LI are born encased in a hyperkeratotic translucent membrane, known as collodion baby, and within 2 weeks develop large, thick, brownish lamellar scales with minimal erythema. Additionally, LI is associated with crumpled ears, alopecia, eclabium, and ectropion. Lamellar Ichthyosis (LI) is a rare, hereditary skin condition characterized by dry, thick, fish-like scaling of the skin. Ichthy means "fish" in Greek and lamellar means "thin layer."
Lamellar ichthyosis (LI) is an autosomal recessive disorder that is apparent at birth and is present throughout life. The newborn is born encased in a collodion
membrane that sheds within days. The shedding of the membrane reveals generalized scaling with variable redness of the skin. The scaling may be fine or platelike, resembling fish skin. Although the disorder is not life threatening, it is quite disfiguring and causes considerable psychological stress to affected patients.

6. Eyelids. Mortality/Morbidity
In the neonatal period, following the shedding of the collodion membrane, the newborn is at risk for secondary sepsis and hypernatremic dehydration.
The membrane sheds within days and large, thick, brownish lamellar scales develop.

7. The child after 2 months showing lamellar ichthyosis
As the child ages, the hyperkeratosis can interfere with normal sweat gland function, which can predispose to heat intolerance and possible heat shock.Ectropion may result in the inability to fully close the eyelids and can cause exposure keratitis.
The child after 2 months showing lamellar ichthyosis
(Aradhya et al. Clinical outcome of collodion baby: A retrospective review. Indian J Dermatol Venereol Leprol 2013;79:553)

8. TGM1 gene TGM1 consists of 15 exons
Encodes a 90 kDa, 817-amino-acid protein called transglutaminase-1 (TGase-1)
B-sandwich domain and catalytic core domain = catalysis. Coding exons TGM1 is normally expressed in the suprabasal cells of stratifying epithelia such as epidermis, the upper digestive tract, the female lower genital tract and in the endometrial epithelium late in pregnancy

9. Transglutaminase 1
Crosslinks proteins by catalyzing Ca2+ dependent formation of isopeptide b/w Glu from one protein and Lys in another.
TGase-1 is responsible for cross-linking of ARP preserver proteins such as involucrin and loricrin during the formation of the cornified cell envelope (CCE)
ARP: actin related proteins

10. Transglutaminase 1
Essential in formation of the cornified cell envelope (CCE).
The CCE, an insoluble structure composed of cross-linked proteins laid down on the inside of the plasma membrane in keratinocytes in the stratum corneum.
The CCE acts as a mechanical barrier and protects against water loss and infectious agents.
CCE: 10–20-nm thick. significant role in the maturation of human epidermal cells by the formation of an isodipeptide cross-linking bond, thus assembling a highly insoluble layer known as cornified cell envelope, which in turn obviates excessive water loss and provides a protective shield against an inhospitable environment.
Childhood and adulthood
Skin: The disease is characterized by generalized scales, which range from fine and white to thick, dark, and platelike. The scales are arranged in a mosaic pattern resembling fish skin. The lesions involve the entire body and are increased in flexural surfaces such as the axilla, groin, antecubital fossa, and neck. The individual scales tend to be larger over the legs and, in some areas, are centrally attached and raised at the edges.[5] See the image below.Keratoderma of the palms in a patient with lamellar ichthyosis. Courtesy of Dirk Elston, MD.
Nail abnormalities: These include secondary dystrophy with nail fold inflammation, subungual hyperkeratosis, and longitudinal or transverse stippling. The nails may grow 2-3 times the normal rate. See the image below.Nail dystrophy and inflammation of the nail folds. Courtesy of M. Bryan, MD.
Scalp: Scarring alopecia can result from the overall tightness of skin and the thick stratum corneum entrapping hairs. The hair may be thin and fine but, similar to the nails, can grow at 2-3 times the normal rate.
Other findings: The lips and mucous membranes tend to be spared. Other associated features are ectropion, eclabium, bilateral conjunctivitis, small and deformed ears, and inflexible digits due to taut skin. See the image below.Inflexible fingers due to taut skin in a young patient with lamellar ichthyosis. Courtesy of Dirk Elston, MD.

11. TGM1 Gene Mutations
From: Farasat et al.

12. Working Flow Diagram
Working flow-diagram
Most Reported Mutations are located in exons: 2,3,4,5,6,7,8,13, 9,10,11,15

13. TGM1 Coding Exons Sequencing
A>C transversion in exon 11
(Reverse T>G)
Most Reported Mutations are located in exons: 2,3,4,5,6,7,8,13
To lesser extent: exons 9,10,11,15
Part of exon 11 sequence: Mutant vs. Normal

14. NCBI blast

15. The detected TGM1 Mutation
NM_ : c.1621A>C
Altered codon 541 from ACC into CCC thus changing the amino acid threonine into proline
P22735: p.T541P

16. It is a germline mutation
The detected TGM1 exon 11 missense mutation. (a) the normal sequence (b) the homozygous c.A1621C mutantion (c) one of the heterozygous parents . The arrow indicates the mutation site.

17. Is it a known mutation?
HGMD
Ensembl variation table
Literature
Novel

18. SIFT Results (Batch Protein)
Is it pathogenic?
SIFT Results (Batch Protein)
Protein ID Substitution dbSNP ID Prediction Score Median Info Number of Seqs at position Comments
CCDS T541P novel DAMAGING  
* Low confidence means that the protein alignment does not have enough sequence diversity. Because the position artifically appears to be conserved, an amino acid may incorrectly predicted to be damaging. (

19. PolyPhen-2 report for P22735 T541P
Query
Protein Acc Position AA1 AA2 Description
P T P Canonical; RecName: Full=Protein-glutamine gamma-glutamyltransferase K; EC= ; AltName: Full=Epidermal TGase; AltName: Full=Transglutaminase K; Short=TG(K); Short=TGK; Short=TGase K; AltName: Full=Transglutaminase-1; Short=TGase-1; Length: 817
Results
Prediction/Confidence   PolyPhen-2 v2.2.2r398
HumDiv
This mutation is predicted to be PROBABLY DAMAGING with a score of 0.998 (sensitivity: 0.27; specificity: 0.99) (

21. GTLIVTKAISSNMREDITYLYKHPEGSDAERKAVETAAAHGSKPNVYANRG
Human
Chimpanzee
Macaca
Guinea pig
Mouse
Dog
Rat
GTLIVTKAISSNMREDITYLYKHPEGSDAERKAVETAAAHGSKPNVYANRG
GTLIVTKAI-SNMREDITYLYKHPEGSDAERKAVETAAAHGSKPNVYANRG
GTLIVTKAISSNMREDIT++YKHPEGS+AERKAVETAAAHGSKPNVYA-R-
GTLIVTKAI-SN-REDIT++YKHPEGS+AER+AVE-AAAHGSKPNVYA-R-
GTLIVTKA+-SNM++D+T++YKHPEGS+AERKAVETAAAHGSKPNVY-NR-
GTLIVTKAI+SNMREDIT++YKHPEGS+AERKAVE-AAAHGSKPNVYA-R-
Comparisons include human, common chimpanzee, macaca, guine pig, mouse, dog and rat. Shaded amino acid (T) is the amino acid altered by the mutation.
TGase-1 partial amino acid sequence (residues 524 to 574) alignments from a motif of the catalytic core domain. The amino acid sequence alignment by using the NCBI protein Blast analysis (

22. Several lines of evidence suggest the this mutation is pathogenic:
the mutation is inherited from the consanguineous parents and absent in healthy control subjects
amino acid sequence alignment showed that the mutated threonine residue is highly conserved across distant species i.e., it is important for the enzyme activity
the altered amino acid is located in a critical region of the enzyme (the catalytic core domain) and in silico analysis using SIFT and PolyPhen-2 programs predicted that the amino acid change is damaging for the enzyme function
(4) threonine and proline have quite different characteristics: threonine fits into regular secondary structures proline behaves as a structural disruptor
in the middle of regular secondary structural elements. Hence it is believed that proline disrupts the proper folding of TGase-1 enzyme and its catalytic function.

23. PCR-RFLP (HphI) results of the patient (lane 1), his mother and father (lanes 2 and 3, resepcetively), one homozygous normal control subject (lane 4) and a negative (no genomic DNA) control (lane 5). 238 bp, 124/114 bp.
The c.A1621C mutation thus identified abolishes the cutting site of HphI (Haemophilus parahaemolyticus) restriction enzyme therefore, the following PCR primers (TGMF: AGTGACAAGGTGTACTGGCA and TGMR: GAGG TTCCAATTCCCACGTG) were designed to amplify a 238bp fragment encompassing the mutation. HphI digests the normal allele into two fragments (124 and 114 bp fragments) whereas the mutant allele remains uncut. Figure 3 shows a photo of an agarose gel where the patient and his parents' genotypes are indicated. The parents' genotypes confirm their heterozygosity for the mutation (as illustrated by having 3 fragments).

24. Conclusion
ARCI-1 (LI) in the present case is attributed to a novel “p.T541P” mutation in the catalytic core domain of the TGase-1 enzyme.
The study further confirms the involvement of TGM1 mutations in LI.
This finding expands the mutations spectrum of TGM-1 gene and is important for delivering proper counseling and diagnosis opportunities for the proband's family.
- NCBI/ClinVar Accession: SCV
c.1621A>C