DNA isolation, PCR and gel electrophoresis as
methods for detection of known mutations in the
LMNA gene
Kalisvaart, L.
ID: i6215145
Tutorial group 27
Faculty of Health, Medicine and Life Sciences (FHML)
Maastricht University
Course BBS1004
25th May, 2020
1
, 1. Introduction
A genome wide genetic and mutational profile of a fetus can be determined via sequencing
of maternal plasma DNA and is used to perform preimplantation genetic testing.
Preimplantation genetic testing is an example of screening methods that are used to detect
monogenic diseases(1). Monogenic diseases are the result of a single gene mutation in the
autosomes of an individual. Monogenic diseases can be inherited via autosomal dominant,
autosomal recessive and X-linked inheritance patterns or can be developed during lifetime
due to environmental exposure(2).
Laminopathies are monogenic diseases that are caused by these single-gene mutations in
the lamin gene. Lamins are fibrous proteins in the type V intermediate filament that are
located on the inner membrane of the nucleus where they polymerize to form the nuclear
lamina. The nuclear lamina is a meshwork of intermediate filaments located between the
inner nuclear membrane and chromatin. The nuclear lamina has a fundamental role in the
organisation of the nucleus by regulating the heterochromatin structure, positioning of the
nuclear pores and by disassembling and reforming of the nuclear envelope during mitosis(3).
In humans the B-type lamins are encoded by two genes which are constitutively expressed in
somatic cells. The LMNA gene encodes for A-type lamins, including the major somatic cell
isoforms lamins A and C(4). This specific LMNA gene encodes for proteins that have an
important function in fat storage and in the development and function of adipocytes.
Mutations in the LMNA gene have been shown to cause several different inherited diseases
in nearly all somatic cells and can either affect striated muscle, adipocytes, peripheral nerves
or cause features of premature aging. However, in the disease Hutchinson-Gilford progeria
single gene mutation occur during early embryonic development causing the effects to be
more generalized and can’t be inherited as the individuals premature age and die too young
to reproduce(4).
On the contrary, in diseases as Emery-Dreifuss muscular dystrophy (EDMD) and Familial
partial lipodystrophy (FPL) the effects of the mutation in the LMNA gene are tissue-specific.
EDMD is a genetically heterogeneous condition and it is characterized by early contractures
of the Achilles tendons, elbows and post-cervical muscles, slowly progressive weakening of
the muscle wasting and cardiac conduction defects(5). EDMD is caused by a R453W
mutation on the LMNA gene. This abbreviation implies that the arginine amino acid on place
453 in the DNA strand is changed to amino acid tryptophane. The codon for arginine is CGG,
so a point mutation causes the C to be mutated to a T to form tryptophan.
by a change in base due to a point mutation.
2
methods for detection of known mutations in the
LMNA gene
Kalisvaart, L.
ID: i6215145
Tutorial group 27
Faculty of Health, Medicine and Life Sciences (FHML)
Maastricht University
Course BBS1004
25th May, 2020
1
, 1. Introduction
A genome wide genetic and mutational profile of a fetus can be determined via sequencing
of maternal plasma DNA and is used to perform preimplantation genetic testing.
Preimplantation genetic testing is an example of screening methods that are used to detect
monogenic diseases(1). Monogenic diseases are the result of a single gene mutation in the
autosomes of an individual. Monogenic diseases can be inherited via autosomal dominant,
autosomal recessive and X-linked inheritance patterns or can be developed during lifetime
due to environmental exposure(2).
Laminopathies are monogenic diseases that are caused by these single-gene mutations in
the lamin gene. Lamins are fibrous proteins in the type V intermediate filament that are
located on the inner membrane of the nucleus where they polymerize to form the nuclear
lamina. The nuclear lamina is a meshwork of intermediate filaments located between the
inner nuclear membrane and chromatin. The nuclear lamina has a fundamental role in the
organisation of the nucleus by regulating the heterochromatin structure, positioning of the
nuclear pores and by disassembling and reforming of the nuclear envelope during mitosis(3).
In humans the B-type lamins are encoded by two genes which are constitutively expressed in
somatic cells. The LMNA gene encodes for A-type lamins, including the major somatic cell
isoforms lamins A and C(4). This specific LMNA gene encodes for proteins that have an
important function in fat storage and in the development and function of adipocytes.
Mutations in the LMNA gene have been shown to cause several different inherited diseases
in nearly all somatic cells and can either affect striated muscle, adipocytes, peripheral nerves
or cause features of premature aging. However, in the disease Hutchinson-Gilford progeria
single gene mutation occur during early embryonic development causing the effects to be
more generalized and can’t be inherited as the individuals premature age and die too young
to reproduce(4).
On the contrary, in diseases as Emery-Dreifuss muscular dystrophy (EDMD) and Familial
partial lipodystrophy (FPL) the effects of the mutation in the LMNA gene are tissue-specific.
EDMD is a genetically heterogeneous condition and it is characterized by early contractures
of the Achilles tendons, elbows and post-cervical muscles, slowly progressive weakening of
the muscle wasting and cardiac conduction defects(5). EDMD is caused by a R453W
mutation on the LMNA gene. This abbreviation implies that the arginine amino acid on place
453 in the DNA strand is changed to amino acid tryptophane. The codon for arginine is CGG,
so a point mutation causes the C to be mutated to a T to form tryptophan.
by a change in base due to a point mutation.
2
